Actually, GOG's webpage has it listed as compatible with "Windows XP & Windows Vista (32 & 64 bit)".

Anyway, with a relatively painless workaround for the 4GB+ RAM performance problems, the game is compatible with 64 bit Windows (incompatible would imply it didn't work at all). GOG (etc) may have a list of known issues, or an asterisk by the mention of 64 bit support, etc, when they update the page for the re-release the game.