This version should be pretty close to final. I hope Jeff Dike will include it 
in the next 2.4 UML release.

Changes:
- tdb keys are now safe not to ever collide,
- Humfs now supports unmounting (that makes meta_tdb fully operational),
- fixed some bugs.

Simple program to list metadata from tdb file is included (tdbfsck).

Metadata structure kept in tdb may still change in an uncompatible way.

Patch also available at:
http://kem.p.lodz.pl/~peter/humfs-2.4.26-1-meta_tdb-2.patch.bz2

ps. Thanks to Oleg Drokin for reviewing my code.