I own this game on both GOG and Steam. When you launch the GOG version, either directly from the executable or Galaxy, it will load up the Steam API as if you launched the game through Steam (Overlay, unlocking items, etc.). I tried to delete the Steam files but the game errors out after doing that. Does anyone know of a way to get rid of this functionality so it doesn't "phone home" to Steam?

Possibly relevant? https://www.gog.com/forum/general/akibas_trip_undead_and_undressed_is_a_steamrip

Yep, that's the exact behavior. I'm not as offended as that guy is, but it is kinda weird it does this. I've found that having Steam closed before starting to play prohibits the Steam stuff from starting up, so I guess that works for me. Thanks for providing the link!