is it still a thing? Had plans to grab this one on GoG, but my friend reported me recently, that stable version there is still 0.5.32.
No, the latest stable GOG realease is 0.16.36 (See my above post).
The latest standalone GOG installer is still 0.15.32, but will be updated to 0.16.36 whenever GOG bothers to release it.
Also - is there any difference between GoG's binaries and ones from dev's site? I mean - are they drm-free too and require key just to download, access mod portal and multiplayer?
Not really, the GOG one comes with a GOG icon, that's pretty much it. If you get it from GOG, you also get access to the one on the dev's site anyway.