Main page for Sun Studio and Sun Studio Express can now be found at http://www.oracle.com/technetwork/server-storage/solarisstudio/overview/index.html
As I'm getting some odd 404 errors and pages moving around browsing TechNet, here's a link to the Legal readmes for SunStudio 12:
As I understand it this means if you already have Sun Studio you are licensed and are able to distribute your binaries. It also seems to say it's fine to share it with fellow developers and 'researchers':Permitted Use: You may reproduce and use the Software for
Individual, Commercial, and Research and Instructional Use,
subject to and conditioned on Your compliance with the
Additional Terms below.