I watched a video of Duke Caribbean : Life's A Beach and it looked brilliant. However, you can't buy it off GOG.com, the same with the other official expansions. Will they ever come to GOG.com or have CD Projekt tried and failed at doing so? I could buy the expansions off eBay but they would be very hard to install. Also, if they came to GOG.com, would they work on eDuke32? I will appreciate any answers you can give me.
There have been a number of threads posted regarding the expansions. But to put it simply, they are not official in the sense of them being by Apogee / 3D Realms as they were by third parties. Because of this, getting their licenses is most likely a nightmare for GOG so don't hold up any hopes of getting them here.
If you do get them from eBay, bear in mind that their format will be incompatible, so you'll need to get an extractor to get the grp files out of them. Once done you can then use them with eDuke32. Google should help you find an extractor.