A member of the SunHELP Rescue list details in this mailing list post his attempts to purchase a license for Solaris 10 from Oracle.
If you want to purchase a Solaris 10 license (which is NOT the same as a Support Contract), all you have to do is buy a Solaris 10 “Media Pack”.
“The Solaris 10 license is bundled into the media pack (it is on a component CD). Therefore, this license comes free with the media pack purchase. While the agreement text is a little confusing, the moment you receive the media pack and open it, you will no longer be operating under trial terms.”