Would GOG ever consider letting us back up our copies of the Dungeons and Dragons Anthology, similar to what they did for The Witcher? I don't even know if it's possible, but it would be really nice, so I don't need the DVD to install the games.

I'd say zero chance. The Witcher games are done by CDProjekt Red, which is owned by CDProjekt, also owners of GOG. So there's a connection there that there isn't with any other games.

Anything's possible, but to this point, there's been no indication that GOG is looking at this as an option, or even that they want to. I doubt the publishers would agree to it anyway. Steam is its own form of DRM, but the games here are DRM free, so giving the backup option would be seen by many people as a free game they can just give away. Hell, many people are looking at the backup Witcher games this way already.

Well if the anthology comes with a CD key its possible, but I doubt that GOG would ever do it. They really have little incentive to do so.