The demo thats currently on nebula its modifed and intended to run with the fs2 rootpack + mvps.
So what about for the people who dont have the FS2 rootpack installed, there is no demo avalible.
So im thinking about two possible solutions here:
1) Create the fs2demo rootpack and copy the demo there, it would have to be the unmodified demo.
2) Handle it in-launcher, hardcode a "fs2 demo download" that downloads the demo from the internet
(its avalible at archive.org) https://archive.org/download/Freespace2_1020/fs2demo10.zip
And install it as it would be a regular rootpack.
I can do both, altrought the second one will be only be avalible for my new version of the launcher.
oh, and BTW, 21.0.0 is the last version that can run the demo.