Where do I get it?

The best bet is to check out the GIMP home page which includes pointers to the latest source, as well as complete binaries for a variety of platforms, including at least Linux (a.out and ELF), FreeBSD-2.1, HP-UX, SunOS and Solaris 2.4, and SGI. More may be available by now; go check the web page. Go on! Vamoose! You can come back here after you get it!