A good place to check out for any kind of Solaris compatible software, is
www.sunfreeware.com. They usually have alot of the software you are used to on Linux ported to Solaris. I don't see aim on the list there, but you may be able to download source code for aim and compile it yourself (wouldn't be very user-friendly though).
I'm not familiar with this superchat file, so I don't think I could help you with the file other than to try and run it on a command line like;
java jsuperchat.jnlp
