I guess it's more or less expected with open-source hardware designs. Why bother going to open-source hardware the application you meant for it requires the purchase of a commercial OS? -- You might as well buy closed-sourced hardware at that point, as there are plenty of perfectly good single-board computers that run Windows or QNX or other commercial OSes.
Actually I think that the majority of GPS navigation systems (the aftermarket ones for cars) run Linux -- they just license the maps directly from TeleAtlas or NavTech, and have the volume/money to make it viable.
---Joel