Just tested out GOG and STEAM server discovery with the help of Mr. Monday. Turns out that SuperPower2 connects to the same matchmaking/discovery server (the server that sends you all of the active games so you can connect to them), so GOG users can play with STEAM users and vice versa. The details; Using a packet sniffer (Wireshark), I was able to manually inspect outgoing and incoming packets. After a little bit of snooping, I found 'gateway.nordic.rankedgaming.com' on an incoming packet. This suggested that Steam and GOG did in fact share a matchmaking server. I gave Mr. Monday a shout with his steam version and he graciously checked his server browser, and we compared against mine. He then set up a game using the Steam version, and I connected on my GOG version successfully. Hope that helps with any doubts you have about buying either version!
