Hi,
I added notes on the PCB footprint file format to the PCB Quick Reference on the wiki at:
http://geda.seul.org/dokuwiki/doku.php?id=geda:pcb-quick_reference
The goal is to help users write their own footprints and have quick access to the easy-to-forget parts of the file-format. Like what flags and 'clearance/2' means.
Please post or make additions and edits!
One thing I'd change is the part which says:
-Dan