rosegarden musE and linux multimedia studio are all free and got copyright free samples
but I have not tested any on windows.
I understand what you mean about the samples and loops provided by most free sequencers, but for the sake of this competition, I would hope that nobody would submit a bunch of loops mashed together, regardless of how good the result is.
On the contrary, I think that everyone should be allowed to produce any kind of music using any kind of method they want. In fact, I
encourage people to use free software and free loops because if we limit this competition to people playing real instruments, we would get 5-6 submissions.
With our video competitions, the problem has always been that most people lack the skills and/or resources to produce a video. Same thing could easily happen here, which is why it would be a good idea to include some useful links to the first post, to help people get started. Optimal would be a free software that had all the loops/instruments needed.
Even if the final result is crap, the person still has a change to participate in this competition without having played the violin 8 hours a day for the last 12 years. The competition should be more about fun than about some "serious" music production where newbie tracks are laughed at.