For those of you who don't know, The "Homeworld Remastered Collection" on Gog contains a remastered version and a classic version for Homeworld's 1 & 2. Multiplayer, however, is only available for the remastered versions. For some reason Gearbox decided to leave it out of the classic versions.

Doing some searching on the web, I found a mod for the Steam version that re-adds multiplayer to "Homeworld 2 Classic", but I can't seem to find a download link so that I can apply it to my Gog version. Does anyone know if this mod or a similar mod is available to download somewhere so that I can get classic multiplayer put back into the Gog version?

You could probably contact the mod author and ask if they will make the mod available to GOG.com users. Failing that, try asking the bulk of the modding community on the GBX Forums and see if they will make a copy available for GOG.com users.

The GBX Forums can be found here: https://forums.gearboxsoftware.com

Finally got around to trying this and it does re-add the multiplayer back to the first game but not the second game. Close enough to award you the solution. :)