Most radio functionality still requires closed-source binary blobs, almost certainly containing backdoors. There's no such thing as open source CDMA drivers and the only open source GSM driver (OsmocomBB) is basically abandon-ware at this point. 4G and LTE are simply not going to happen.

Would be really awesome to see more support for OsmocomBB and similar projects though.

Here are some neat slides from a presentation on OsmocomBB from last year for anyone interested: http://elinux.org/images/9/9a/Getting_the_First_Open_Source_...