Emporer: Battle for Dune was their first 3D RTS and I personally loved the gameplay, story, and soundtrack. I very much hope it will eventually be open-sourced.
I really liked that game, it had a lot of strategy to it and a decent story.
The multiplayer had a common key bug that made it hard on some maps. The atreides airdrones could fly at the edge of the map and not be targeted, and take out the harvester carryalls / and other air units
There were claims of a flame tank bug that could target any unit that was mentioned on the forums much much later, but I don't know if the details were ever revealed, I never figured it out so I guess its just theoretical..
Yeah, I wonder why Emperor: Battle for Dune is not part of the open source since it's basically an earlier version of the General Engine. Would be weird to have the source code for that but not for Emperor.