I was just digging through some old news I marked down but never read, and just noticed the release of an open-source, reference SIP stack that engineers can tap when developing VoIP and other SIP-enabled equipment designs. The effort seems to be progressing through an organization called SIPfoundry. Here’s an excerpt from their mission statement:
The mission of SIPfoundry is to promote and advance SIP-related Open Source projects. Through SIPfoundry the users, developers, and distributors of SIP based products can collectively support each other and accelerate the growth and adoption of SIP.
I’ve mentioned SIP before, and I’m still pretty excited about what SIP could do in the mobile environment - if it made it out into more implementations. However, I haven’t seen it out in the wild yet. Hopefully that’s just because it takes time to deploy a new capability and not because there is interest in keeping it out of the public marketplace.