AmigaOS is still not free, but you can legally download it, if you own an amiga. If those amigas are fully orginal, then you need: AmigaOS/workbench 1.2/1.3 for the a500, workbench 2.x for the a600. try searching around on google for the adf files.
There is a little prob though, since the pc floppy controller is incompitable with the amiga one, you gotta find a way to transfer it over to the amiga via a serial/null modem cable.
So i think it would be easier to just buy it from somewhere.
