I am, however, pursuing a project seeking to put together a new firmware for Calypso-based "dumbphones" that would function just like the original proprietary fw, intended for using the phone "normally" as an everyday phone, unlike OsmocomBB which is intended for hacking and security research instead. FreeCalypso is the name of my project, and it's being developed in this Mercurial repository:
I am very excited to hear about this project. If it is possible to alter the 45 MHz tx/rx separation of the E-GSM-900 band on both a handset and BTS, I believe that in conjunction with a few other modifications, it might be possible to legally run a GSM network in the ITU Region 2 33 cm amateur band. While not necessarily especially practical, that could be a fun little project.
Once I get layer23/mobile working, I plan to test this in conjunction with calypso-bts. If it works, it would be cool to be able to do it on an untethered handset.
Rusty D