But its details are here: The macfuse google code project page
And it looks like a good thing indeed!  Being able to use the Linux fuse file systems on OSX will make for a wild ride, and really open a lot of doors

Here are just a few Fuse based file systems:

• The S3InfiniDisk File System
• The Wayback File System
• The NTFSMount File System
• The MySQLfs File System

Needless to say, the number of things that have been (and can be) done via fuse makes its adoption on the Mac a very exciting idea.