I think the project is a great idea, and I have both a personal and 
professional interest in seeing a free (==BSD) implementation of such a 
block device.

While googling around on the subject, I got the impression that the sole 
reason such implementations don't exist already is that M-Systems have 
pretty much patented the whole idea, as obvious and necessary as it may 
be to use NAND flash.

Does anyone know the exact scope of the patent, and how to get around it?

There also appears to be a similar patent in Europe:
http://gauss.ffii.org/PatentView/EP770960

Regards,
ali