I don't believe it's just open firmware, but I think it's also an open hardware project. While perhaps not as slick as yubikey, I do have several solo keys and

I don't believe it's just open firmware, but I think it's also an open hardware project. While perhaps not as slick as yubikey, I do have several solo keys and they're great. Only real complaint is I wasn't able to get the NFC working, which I believe is a common issue, and I think they were working on an updated design that should work more widely with a range of devices.