You can grab, play with and use YAFFS free of charge right now from CVS.
If you sell a product using it you must release Source code as well as Binary code under the GPL. If you do not wish to disclose your Source Code see the FAQs and this discussion.
YAFFS Licences are non-exclusive, perpetual, world-wide, royalty-free and paid for with a single fee for one product. A Licence entitles you to most further development and improvement of the YAFFS code.
You can find further information about each licence in these documents:
You can do a lot to get going with YAFFS on your own, using the resources of this site. If you are serious about using it you should join the Mailing List.
If you have simple questions post them to the List; you will find a helpful and supportive group of colleagues, as well as a searchable archive.
If you need more help we can provide consulting services to you, as we have to many Licence-holders. Our usual rate is GB£600/day, reducing for longer-term work.
Documents about the development and use of YAFFS: