All I keep thinking as I try to make my way through these pages and pages of text... is... "what does IP stand for"?

Incorrect.
They are original works inspired by both Roadside Picnic and Tarkovsky's film Stalker (inspired by the novella). The games fall under fair use terms of copyright as they are at most transformative works, but were also officially recognised by the Strugatsky brothers - to the point where they in turn wrote another book based upon the unvierse as shown in Shadow of Chernobyl.

Many things shown in the novella, film, games are common themes in science fiction and are as such not specific to them. Anomalies, for instance, have also appeared in the Metro series.

I suspect the litigation you are referring to is between Deep Silver and GSC / some other parties. Deep Silver allegedly had not (perhaps still have not) paid money owed to GSC, Deep Silver also wanted to take legal action against GSC as after the death of Boris Strugatsky, they quickly ran in and attempted to buy the S.T.A.L.K.E.R. IP.
What they actually bought was a licence to base media directly upon Roadside Picnic yet they didnt seem to understand that - even when faced with the fact that neither Strugatsky had any claim to the S.T.A.L.K.E.R. IP in the first place.
They weren't the only company to have made such a folly either. Several other companies have laid claim to it (two in the sell off period of THQ).

Intellectual Property (not to be confused with Internet Protocol - as in 'IP Address')

http://en.wikipedia.org/wiki/Intellectual_property

The trade marking and copyrighting of characters, series and 'universes'

Not Deep Silver, but bitComposer Games.

Damn link wont load for me (my net is poo right now).
Damn sure GSC are still chasing money from deep silver though...

Not even this one?

that ones working! :)

Screamer 4X4 - yep says 'licensed' right there on the GOG game card page! Added to the 'cars and marques' section Again goes to show how much this one isn't really part of the 'Screamer' series at all because the rest had fictional vehicles, I'm pretty sure
Also, no WAY did I just get to write 'Mastertronic' right under 'Codemasters' - is this 2014 or 1984?

Amerzone - hmmm interesting, good spot, I've gone for the 'Not external IP' section but the entry is a bit 'I don't know for certain' if you read it - thanks for that!

F-1117A - Yeah, potential licensed fighter aircraft and guns are a major issue for both this and my other list - really hard to know. In this case I have F-1117A on my GOG shelf so I downloaded the pdf of the manual and scoured the 'copyright' and 'credits' sections but it only mentioned MicroProse, no mention of 'Used under license from Lockheed Martin' or anything like that so I'll leave it off - may have to check the manuals of other plane games I have on here though...

Aye thats the case!
There are still people out there in the belief that GSC are closed and Bethesda actually have the rights (neither true).
MADNESS I TELL YOU!

Sorry if you think my entry is a bit 'Chinese Whispers' -ish but what should I put in 2 or 3 lines? Is it mainly that I put 'Loosely based on' instead of 'inspired by'?

...though THIS also suggests that they dont have a fucking clue (posted the day before the link you provided).

"Boris Strugatsky, one of two brothers that brought the novel adaptation of the film, Stalker, to life, passed away on November 19. All other rights to the "Stalker" or Roadside Picnic universe outside of video game adaptations belong to the brother, Arkady Strugatsky."

Edit: and the image on the link you shared is by Feng Zhu and is simply part of a painting demo he did - yet they havent accredited him in any way (the image solely being hosted on his blog). O____o
heheh! pretty much, yeah. ;)
i think the best phrase would have been "transformative work(s) inspired by..."

That's some fine mess alright. Interestingly, up to some months ago, GamersGate was selling a non-standalone version of Call of Pripyat published by bitComposer Games. Now, this version seems to have gone the way of the dodo and the only version available is the standalone one, published by GSC.

OK I changed it to read
"The S.T.A.L.K.E.R games are transformative works inspired by the film 'Stalker' and the novel that THAT is based on 'Roadside Picnic' but nothing was officially licensed."

Yeah, that's the one I was talking about. Or, actually that one (with proper Internet Wayback Machine support :)). Anyway, enough derailing from me too. :P