Seems like dhara.c was integrated into mainline, but they didn't submit
support to YAFFS (if I remember correctly it was because YAFFS requires
license payment for commercial usage).
There no references to either under fs/.
The YAFFS website is not responding. This is what I get about licensing
from Wikipedia:
"The YAFFS codebase is licensed both under the GPL
<https://en.wikipedia.org/wiki/GNU_General_Public_License> and under
per-product licenses available from Aleph One."
https://en.wikipedia.org/wiki/YAFFS
Neither of those are compatible with NuttX in the source tree.