I've only ever used QEMU and Wine, and only with the vaguest idea of how they
work at that, but I suspect there are good reasons to believe no proprietary
software would be required.
Wine, standing for Wine Is Not an Emulator, isn't an emulator per se- it's a
compatibility layer. As such, it requires no BIOS at all. I don't know about
the others, although other compatibility layers would likely be the same.
As for VMs, a BIOS blob is required, but there are a good number of free
BIOSes available. QEMU uses the libre SeaBIOS by default, if I remember
correctly- similar situations likely apply to others.
Regardless, that's what I *think* is the case. It may be completely wrong,
but all are listed in Trisquel's repos, which suggests they're at least all
free :).
