Not the 1984 Infocom one written by Douglas Adams and Steve Meretzky, but the Supersoft one by Bob Chappell.
We haven’t had much yet at this blog on legal tangles; the history of adventures is not chock-full of them like, say, Atari. I’ve skipped over EduWare’s Space I and Space II games despite them being listed at the Interactive Fiction Database as they are really RPGs (the CRPG Addict covered them here) and they were even based so much on a pencil-and-paper RPG (Traveler) that Game Designers’ Workshop dropped a cease-and-desist. I also didn’t mention how with The Prisoner (by the same company!) the producers got permission from ITC Entertainment to open a Prisoner-themed restaurant (??) hoping that would be sufficient cover. Other similar violations were generally done with a computer-games-aren’t-that-big-let’s-hope-they-don’t-notice stance. (This is how Atari was in contrast — it started making “real money” early, and roughly the same time all this was happening they sold millions of copies of Space Invaders for the Atari 2600, as opposed to thousands or hundreds.)

The original version (the tape picture from earlier) was for Commodore’s earliest computer, the PET. This screenshot is for the later C64 version.
It’s certainly tempting to look at the opening screenshot “with kind permission of Douglas Adams and Pan Books” and be skeptical, but at least the Pan Books part was true: Bob Chappell wrote a letter asking if he could make a game based on Hitchhiker’s and they sent back a letter saying yes. After finishing his game he sold it to Supersoft for “500 pounds worth of equipment and assorted programs”. Keep in mind this is extremely early in the UK commercial adventure game market; Hitch Hiker’s was first advertised Summer of 1981 around when most of the other releases I’ve highlighted (like Planet of Death) landed (one earlier game, Catacombs — first advertised March 1981 — was also by Supersoft, although it isn’t available for download). So we’re talking about a request for a license at the very tip of an industry, it is understandable they were a little informal with it.
As Supersoft in 1983 tried to come out with versions of the game for Commodore 64, Vic-20, and Dragon, Douglas Adams’s agent Ed Victor came knocking; a settlement was made out of court, and Pan Books footed the legal consultation bill, so it wasn’t like there was simple amateur confusion going on, just it was easier to avoid a legal fight altogether and settle. It is possible Supersoft had a leg to stand on but Douglas Adams himself wasn’t involved in the original deal, implying shaky ground; it is also possible based on the wording of the letter the rights only applied to Chappell’s original PET version of the game but the physical letter hasn’t surfaced to confirm or deny this.
Unsold copies of “Hitch Hiker’s” was destroyed as part of the settlement and the game was put back onto the market later as Cosmic Capers. (Incidentally, the weird anomaly of Galactic Hitchhiker which I covered last time went entirely untouched by the legal stick, but it stayed on the fringe system of the UK101. No doubt had an attempt been made to republish it would have raised the legal sirens.)

Additionally, the somewhat … unimpressive … text and interaction of the game is still fitting in with most of the product in the UK at the time. You can see what feels to modern eyes like a modern-shovelware-grab-bag, but for the time was a normal commercial game written in BASIC.
Based on a December 1981 review from Computer & Video Games magazine it wasn’t ill-regarded (“a well thought-out attempt to reproduce the imaginative radio/T.V. series”); this is, simply put, yet another typical-for-the-market minimalist treasure hunt with a light dusting of Hitchhiker’s.

Having said all that, I can’t defend the end result. I’m not having a good time so far.

My no-doubt incomplete map of the starting area.
You start in a Quiet English Village near a Five Artefacts Inn (where I presume the “treasures” go) and find, minimalistically and randomly, a white mouse — no doubt one of the hyperintelligent ones involved in the compute that answered the Ultimate Question — a rusty car engine (marked as being an Improbability Drive that is made in Hong Kong), a bowl of petunias, the Encyclopedia Galactica, a Vogon Battle Cruiser (shown above) and The Heart of Gold (also inexplicably parked nearby).

There’s a Kil-O-Zap energy gun I found that I attempted to use on the Vogon captain here. No luck getting by yet. The “set” is the Galactic Encyclopedia, and there doesn’t seem to be a way to read any entries other than the one about aquatic bipeds.
The Heart of Gold does not resemble that from the books/radio show/play/etc. and is mostly just a maze.

The maze has an energy gun (which I already mentioned but haven’t used yet), an Arcturian MegaDonkey steak, some keys that appeared randomly, and a cheque signed by Zaphod Beeblebrox that I assumes is one of the Treasures. There’s also a very tempting lever:

PULL LEVER only is bad at randomized times. (I tried to see if some item I could hold affected it, but no — you just wait for the dice roll to go your way.) When it does trigger, you get zapped into outer space, rather like the scene in Galactic Hitchhiker where you need to wave a scarf, except here there is no scarf.

Maybe that direction is a dead end? You do get a number of turns floating in space before death which strongly suggests there’s some way of flagging down a passing ship, but I don’t even have my towel with me, and WAVE isn’t a recognized verb besides. Other than the typical “go”, “get”, and “drop” there’s just
READ, OPEN, CLOSE, KILL, SHOOT, PUSH, PULL, SAY, PANIC
which isn’t much to work with. At some level having less options to test is nice, but the situation is too heavily constrained as is on the window it shows the player; the least it could do is allow the player a few extra actions for breathing room.
Given only the Vogon captain to work on otherwise there isn’t much for me to whack at, but I’m going to keep trudging at this a bit longer before giving up. I’m not sure why I’m putting so much solving energy into such a dodgy game, but I guess I found the story of its creation a little more motivating than normal. (I’ll still take hints in ROT13 format if anyone wants to give them.)
The most cunning thing about Supersoft’s version of The Hitch Hiker’s Guide to the Galaxy might not even appear that much from someone approaching from afar, but as someone who has now trudged through far too many treasure hunts (collect X items, place in position Y) once I caught on to what trick the game was pulling my thought was “oho, that’s even thematic”.
You see, my thought last time that you’d collect items in the “Five Artefacts Inn” was correct. My thought that the cheque from Zaphod Beeblebrox was going to be one of the items was wrong — in fact, the game isn’t asking you to collect treasures in a traditional sense, but “artefacts”. What five items would you consider the most valuable to you? Would they necessarily be the most expensive? In the Hitchhiker’s universe, you probably can even guess what one of the items is.
Speaking of the Hitchhiker’s universe…
…fan-fiction can be something of a writing “cheat”, by invoking deep characters without doing much work; just a minimalist-style mention of an established character can unlock images and associations that weren’t really “earned” by the author. That’s not necessarily a bad thing in context, and it means a scene like something like the Bugblatter Beast (as shown above) might merit an extra mark or two in mental vividness, as would a mention of a babel fish, or Marvin the paranoid robot.
The game just doesn’t have enough disk space to ramble on about the weird gimmick of Peril-Sensitive Sunglasses or the terribleness of Vogon poetry and resorts to shorthand (although it does have a piece of graffiti regarding an “Ode to a Lump of Green Putty I Found In My Armpit One Morning”). It isn’t good or even recommended, but at least it’s understandable.
…
So one of of pieces I was stuck on — the Vogon captain that was stopping me — I simply had neglected to look at the gun, which stated it was OFF and then — well, in the bizarre manner of the two-word parser, the command to switch it on was ON GUN.

Nearby I found a book of Vogon poetry, and a “navigation room” unlocked by the keys I found last time. (Incidentally, I only realized this much later after checking a walkthrough, but the keys came from the bowl of petunias. If you pick the bowl up and drop it again the keys show up, and I had used the bowl to map a room of the maze in the Heart of Gold, so by appearances the keys just randomly materialized in the maze.)
The navigation room includes the “lump of green putty” graffiti, and on a whim I tried to READ POETRY while I was in there.

This causes the ship to move from Earth to Kakrafoon (and if you read the poetry again, back again). The Vogons incidentally start appearing on Kakrafoon and you have to keep the gun handy to shoot them. You need to shoot them the moment they appear — and there can be multiple ones in a row — otherwise they kill you. To add additional distress, the gun has a time limit; if you leave it on long enough it melts away (and you don’t have time to switch between OFF and ON while the Vogons are appearing).
Moving on, I explored Kakrafoon a little…

This bit was much easier than the equivalent puzzle in the Infocom game.
…but was quickly stuck with a Great Green Arkleseizure that is described in a room but you can’t even refer to. With my small verb supply and item supply exhausted, I flew back to Earth and tried poking at the Heart of Gold again.
I did, alas, need to look at hints. I had stuck myself again by the Parallel Universes Problem. There’s a lever that says “don’t pull” so I had tried to PUSH it, and I had also tried dropping the improbability drive from Hong Kong in the same room, and I assumed I had done both at the same time, but apparently not. (I think I had dropped the drive and done PULL, which kills you no matter what — and no, you can’t rescue from being ejected into space, that whole sequence giving you some extra turns to survive was just a red herring.)
Doing things properly causes the Heart of Gold to fly to Betelgeuse, which fortunately does not have any Vogons on it, just a few obtuse locations and puzzles.

The most immediate obstacle is an “Algolian Suntiger” at the “Maximeglon Museum of Diseased Imaginings”, which is defeated via a very special method which actually rises to the level of “good puzzle” presuming you are somewhat familiar with the original Hitchhiker’s series.

There’s at least fair hint that the poetry is execrable from just trying to read the poetry book on its own without knowing the source material, but not “cause all sentient beings to run away” bad.
This is followed by some rapid-fire references, like the Restaurant at the End of the Universe, with a Pan Galactic Gargle Blaster. Remember that cheque from Zaphod Beeblebrox? Here’s where you use it. That’s one expensive drink.

There’s also some shenanigans with a coin that yield some chocolate and cheese-flavored tea. The chocolate is useful in a truly bizarre way.

If you don’t drop the chocolate first the babel fish runs away if you try to get it and the game is softlocked. I had to check the walkthrough for this, and it qualifies as the most random puzzle of the game. Look, the Infocom version of the Babel Fish puzzle is in a way technically harder — certain it involves many more steps, but this one is so baffling and unprovoked I still don’t get it.
You can also get a hint from Deep Thought which happens to be hanging out.

Taking a break from figuring out the Great Question. Maybe if you come at the right time you can get the chocolate explained.
Other than that, I found a towel (horray!), a rubber duck underneath the towel (…ok?), some peril-sensitive sunglasses (which make everything dark so you can see items or room exits and is useless) Marvin the Paranoid Android (who you can try to take, but will run off muttering that he has a “Brain the size of a planet but life’s still depressing”, softlocking the game).
Flying back to Earth, I took a stop by the white mouse that hadn’t been cooperative before and dropped them some cheese-flavored tea. I was then able to pick the mouse up. Then hitching a ride on Vogon Poetry Air again I went back to the Arkelseizure:

If you don’t have the babel fish to hear this, the game is now softlocked.
Past this is an elephant (easily scarable via mouse) yet another tiny maze (not worth even bothering with) and most usefully, a "robot stabilizer" and "The Hitchhiker's Guide to the Galaxy", which informs us DON'T PANIC but otherwise doesn't have useful info.
I admit I was here fairly stumped, other than I realized that while holding the robot stabilizer Marvin was carryable without walking off. I hadn't really figured out the treasures yet, and some experimentation had already indicated some obvious items (like the cheque) didn't boost the score. I just started trying things and found that, the "artefacts" needed are…
…(drum roll please, and maybe you want to predict before I list them)…
…(let me know if you guess all five)…
…the babel fish, the Hitchhiker's Guide, Marvin, the rubber duck (?) and the towel (!). Froody.

With all five safely stowed, you are congratulated with:
Well done! We’ve finished
Well. At least I was not stuck on this game for “13 – 14 years” as noted by Andrew Williams, who wrote a walkthrough.
I will have to say I did “feel” a little bit like I was in some strange variant of the Hitchhiker’s universe. Maybe the off-market one, or a game Ford Prefect himself made in-universe on a lark. What I wouldn’t call it is a cynical cash-in; for its time it was certainly fits in the quality at the time, and even Infocom wasn’t quite Infocom yet.
(Galactic Hitchhiker was still better, though.)