Nick also points out a pair of fan-made projects. Epiar.net hosts Epiar, an open-source "space adventure/combat game". There is a v0.5 demo available for download.
Also, the 4X title FreeOnion has a v0.2 demo and is also an open-source title.
There is also a new version of the MDD (Mercenaries/Damocles/Dion Crisis) Clone. The latest version includes French and Italian translations, as well as having the ability to save and load games.
Lastly, there is a new title called Remnant to the Stars, but I am unable to load that website. Nick writes in his email that the site hosts screenshots and video.