Can Java 5 be installed on any other OS other than OS X 10.5?
This thread indicates one might use the shareware package Pacifist, to unpack and then reuse old Apple installers for Java 5 on Snow Leopard.

Disclaimer: The original author of this comment has no known affiliation or vested interest with the software vendor for Pacifist, nor has actually tried this himself. Still, there seem to be a lot of happy users in the linked thread. :)