Warcraft 2 and Diablo both share the same global. GoG uses a Global Battle Net the made for their game.
They don't offer the ability to download the client either, even tough they do let me download Starcraft, Diablo 2, WC3, go figure.
I tried the key on, but it doesn't work. Thus I'm wondering if it would ever be possible for us to 'activate' our old physical copies of WC2 B.net edition using the CD-Key provided? My CD is so badly preserved I can't even install it, and beside that, the old version of WC2 uses CD as a DRM, you had to play with CD in the drive. Obsessor: I own a collection which includes Diablo, Starcraft, and Warcraft 2: Edition.