System requirements are very modest - any *nix-ish system, gcc, a copy of the jdk, and a plain-text editor. unjava does not impose any licensing restrictions on programs you create. Examples have been updated.
For those who don't know java, but want to move away from being web monkeys, there's a new version of unjava. This release includes automatic jar generation as well as auto-creation of a non-static main class for your project, to reduce "non-static variable cannot be referenced from static context" errors.