Oracle has only change the license to a trail license, why not try it out while you can on both Sparc and AMD after the 90 days you just have to delete it and next time download it again ...
For Solaris 10. Solaris 10 used to have a "download it and use it as long as you want with our blessing" license, with the caveat that it wasn't transferable. Solaris 9 had a "free for educational use" license, and Solaris 8 had a "free license for noncommercial use on uniprocessor-capable machines". Solaris 7 had a $95 program, but I can't remember the details. None of them were transferable, and they didn't apply to other releases of Solaris/SunOS.