Ok. Looks like a bit complex licence: http://swing.fit.cvut.cz/projects/stx/doc/online/english/LICENCE_FREE_STX.html http://swing.fit.cvut.cz/projects/stx/doc/o

Ok. Looks like a bit complex licence: http://swing.fit.cvut.cz/projects/stx/doc/online/english/LICENCE_FREE_STX.html http://swing.fit.cvut.cz/projects/stx/doc/online/english/LIC... But I think you should be able to release free and commercial software with it in general.