The ever productive Régis Montoya has released more goodies:
I’m pleased to share a first release of vp8 codec glue for pjsip. It rely on libvpx from webm project. As usually with contributions from csipsimple it’s only the C code (without toolchain integration as we use a separate one for now). Code style is probably also a little bit crappy but I count on feedback to make this better :).
via VP8 codec post on pjsip mailing list.
As an aside Opus codec integration for pjsip is also available from CSipSimple project.
Enjoy, and join the pjsip mailing list to discuss this with Régis.
pjsip blog 
Hi, I would like to port the pjsip in XMOS platform, do you think it is possible? Thanks. Eddie.
It may be possible. Also I recommend you post these questions to mailing list, the comments on this blog post is not meant for discussion,