After some time with no updates, I’m pleased to announce that there is a demo available! :)
It can be downloaded at http://www.filesavr.com/omegasector - just download and unpack the rar file, and then run the bat file. The jar file is executable as well, but the memory pool needs to be increased from the default, thus the bat.
A little disclaimer: The demo only shows very small portions of what is the scope of the entire game. A demo level with a few different enemies and a couple of weapons is showcased. The complete game will feature a story and plot, as well as a multitude of ships, weapons, and other effects.
But until then, do enjoy the demo :)