"Multiplayer Stalker" is such a pipe dream that it took ten minutes of uninterrupted footage to convince me there was more than a slim chance this will deliver. What I've seen of this standalone mod is enough to turn my head. You too can injure your neck below.
Ray Of Hope developers Infinite Art promise a free, standalone FPS/RPG with the same dynamic world and and vodka-soaked horror you'd expect, with seamless transitions combining all the areas from the original games, plus the bits in between.
I can take or leave the multiplayer. I almost invariably wander off into the night alone in any MMO to do my own weird thing, but they promise more than just bolting more people on, some of which can be seen in the video. A new user interface, roleplay servers, better AI, a reputation system affecting prices and NPC behaviour, with said NPCs being more interesting - "every NPC will have unique dialogue options" is a big project in itself but they're saying it anyway. All this is created "using a modified version" of the X-Ray v1.6 engine developed for Call Of Pripyat.
The bit that I really like the sound of though: two very large maps. Many whatever a hectare is of space. Huge tracts of land. All that lovely (terrifying, miserable) world to hobo around in for days while everyone else is playing efficient nerd soldiers. My flinty heart trembles.
GSC Game World, the studio originally behind the Stalker games, recently insisted that Stalker 2 is still happening, which does raise the ugly possibility that they'll take exception to a project that hews so close to their own eternally resurrecting sequel and borrows so heavily.
It's not clear when Ray Of Hope will be opened up to non-testers, and after nine years in development it's obvious the team are patient. I'll be keeping an eye on its Mod DB page, and I suggest you do too.