[Yaffs] Yaffs direct

I'm currently looking at this nand flash driver.

http://www.samsung.com/Products/Semiconductor/FlashSW/xsr.htm

I guess that Yaffs direct is another option. But I can't seem to get
much information on it nor find out what the licencing costs are.

Can anyone point me in the right direction?
And if we write files with yaffs direct, can we then just read these
using Linux yaffs?

Regards

Ian