You can download the current version of solaris9 or 10
and use it.  There
 is a cdrom version of it, and you only need the first (and maybe the
 second) cdrom if you are only going to crack the root password.  I think
 maybe one of the current sparc versions of solaris may drop support of the
 Ultra 2, so solaris 9 might be a better bet.
 You do have to register an ID of some sort to do a $0 purchase from sun,
 but you need not give credit card or any more information than a
 confirming email address to get that far, assuming you don't actually plan
 to buy anything.  I don't care for the paradigm that you have to "buy"
 free downloads but I guess they can give away their stuff any way they
 want to that way. 
I recently downloaded Solaris 10 to install on my "new" Sunblade 1000, and
thought it was a fairly easy process.  The one strange thing was the
requirement (at least I think it is) to use thier wierd Java app.  OTOH,
that app is pretty cool, and I'm tempted to try and see if I can use it for
other things.
The best part of all this is that you can now download "Sun Studio" for
*FREE*!!!  That means you get their C Compiler, rather than being forced to
use GCC.
On the down side, I can't play with any of this till the weather cools off
significantly :^(
                Zane