How to play online multiplayer ? [License String?]

[Ismaren]

Hello,

I'm trying to find a way to play Zombasite online multiplayer. I'd like to try out the game with some friends. Is it still possible today? What's the procedure to follow?

I bought the game on GOG. When I try to start a non-local multiplayer game, the game asks me for a license number ("Zombasite License String"). I searched the game files and other game-related folders on the computer, including on GOG, but I couldn't find it.

Do you have any idea where can I find it?

Thanks for your help!