When shopping for a software component, it's always useful to be able to try it out before buying.
For your proprietary projects, the GPL version of Yaffs lets you do just that - download it, examine the code and test it out. Check out our documentation and videos.
It's perfectly acceptable and safe to use the GNU GPL code inside your company, providing you don't ship a binary to anyone beyond it. That's when code disclosure and licensing provisions of the GNU GPL kick in. So before you do that, you'll want to talk to us about acquiring a paid Licence.