Tested it today – and indeed, Ring of Marbles works well on Linux (tested on Knoppix). Also, here’s what happens when you release something when you should be sleeping – I said it was open source, but forgot to actually attach the source. So I’m now adding a link to the source as well.
Other than that – Have I mentioned how happy I am with how that turned out? It’s certainly not the most polished thing I’ve ever done, but of all games I made so far, this is the one I enjoy playing the most. Maybe when the LPC is done, I’ll polish it a little and release it as a serious game.
By the way, if there’s a Mac user out there who wants to try to run it and let me know if it works, that could be very nice…

Works on Mac as well (OS X Lion), just double click the Jar.
Thank you! I’ll update the game’s page.