I know its not gog...BUT, you can buy the dos version right from the 3D Realms website! https://3drealms.com/catalog/raptor_23
I'm not sure its the DOS version... look at the system requirements.
I'm quite annoyed that they didn't at least include the DOS version as an extra, or provide the option to install either (like they do with TIE Fighter - you can install three different versions).
I generally prefer to play old games in their "authentic" state, i.e. I don't use higher resolutions than would have been available, I generally use 4:3 resolutions, etc.
It's DOS, I own it. Alternatively, you can buy the DOS version on steam too. It's DRM free on there as well, so you don't need to use the steam client to play.