Does multiplayer work with the Gog version?

Is it compatible with the Steam version?

Im wondering the same thing, given i have it on steam, and i dont see any indication or anything stating it works. Gonna have to ask for the dev to respond to this one. That, and if this game actually is tied to DRM for online play (where as the steam build allows you to host server and play with local builds from steam)

Well, the short answer is "no" and the long answer is "yes".
By default, multiplayer is not supported at all. Upon clicking "Join game" the GoG version of the game shows a "No network" error. (game version 1.0.0.0)

I've read somewhere that the game relies on a Steam dependency/library for multiplayer and that the GoG Galaxy client has their own implementation for it. This means that you can play multiplayer if you launch the game through the GoG client. I assume GoG<->GoG will work, but I'm not 100% sure GoG<->Steam will.

I don't have the GoG client nor will I install it, so I can't confirm any of this. So, if you're like me and don't want to install a launcher then you're stuck with single player until someone makes a multiplayer mod/patch or the developers implement a built-in multiplayer mode.