SUPPORT NOTE:
The Linksys SPA infrastructure is built around a VCD processor chip for which no documentation is available online. Reverse engineering has shown that it has a dual MIPS-X processor, for which no compiler (let alone a free one) is available. Until these important problems are solved, it seems undoably complicated to port this firmware for Linksys systems.
Linksys has of course had a marvelous experience with open source firmware, thanks to the OpenWRT project, so perhaps they will one day join us by sharing what they have on their devices. We will welcome them with open arms: it would be a waste to see their wonderful phones be left behind by more accesible models from competitors.