Kristian: What legal quagmire would that be?
Twice now the forum has eaten my reply so I'll make this quick (and maybe a little unordered).
S.T.A.L.K.E.R. 2 development put on hold due to the dev team abandoning ship and setting up Vostok games. Potential problems due to code and other elements of S2 project / who owns it etc - not definate though.
An independent team began project "Stalker online" - utilising the IP without permission.
Deep Silver alleged to still owe money from distribution.
Nov 2012 sees the death of Boris Strugatsky - who wrote Roadside Picnic with his brother Arkady. Tarkovsky's film Stalker was inspired by / loosely based upon it. They wrote a nother story based upon that. S.T.A.L.K.E.R. was broadly inspired by all of these and Boris Strugatsky (perhaps Arkady too) wrote further work based upon the S.T.A.L.K.E.R. universe. After his death, Deep Silver aquire the rights to make a game based upon / inspired by Roadside Picnic. They dispute this, claiming they have purchased the S.T.A.L.K.E.R. IP. Legal hell ensues.
Further legal action may have also been brought up regarding this by GSC (not confirmed).
Theres a load more too of course -but thats the quick version.
Edit: and for all I know a lot of this has been cleard up now - but it was certainly the case not too long ago.