Landon Fuller has OpenJDK 7 binaries available for testing on Leopard.
Currently it only works for i386 boxes ( and possibly 64 bit machines also, ) at least until Zero works.
You will need to have freetype installed via MacPorts, and have X11.app installed and running if you are running any GUI apps.
Please report all bugs to the BSD porters mailing list.
So far, with the exception of a few GUI bits not drawing properly, it has worked really well.
Well done Landon ( and Kurt and all those other guys who have put in so much time into getting it to run on BSD. )
