The Sun identity server software is available for free via the new free for use push here:
http://www.sun.com/software/solaris/get.jsp
It looks like you still currently need to request a license for it. Its not clear when the source will be available under the related open source push.
https://opensso.dev.java.net/
There is a roadmap for the release of code. I think they want to guage interest in the community.