Firefox OS should be as free as cyanogenmod (basically Android without the
Google malware). A step in the right direction, and something much more
acceptable than any iOS jail based device.
It will still rely on non-free firmware, though.
The 'Trisquel equivalent' for a phone OS would be Replicant, a completely
free mobile OS based on cyanogenmod which replaces any non-free firmware with
liberated ones.
It only supports a few phones at the moment, but they are currently porting
it to Android 4.0, and Galaxy Nexus / SII support is confirmed. This should
help drive the project into public view, for sure.
I recommend visiting http://replicant.us/ for more information.
