SIP SDK For Windows / Windows CE

Hello,

I'm adding a SIP based intercom feature to an existing Windows application. I'd like to use an open-source SIP SDK if there's one that works well. The software runs on either Windows or Windows CE. I've looked at OPAL and think it might work bu I worry about the footprint.

At this point I'd prefer to use something that's L-GPL since I won't be able to share source code from our existing application.

Thanks,
Mike