No, PFS is not free. I registered a long time ago. I was hoping it would continue to be updated but I don't think it has been touched in quite a number of years now.
The reason I asked about SFs is because SFS is another filesystem. One which I have very little to do with and with limited documentation. It sounds as though not too many people know of any differences between the two FS but that sfs may be slower. As for Linux compatibility, I'm sure there's a FFS compilation for it. Even tools for Windows users to look inside a FFS hard disk. Still, if you wanted to run Linux, wouldn't you use Linux filesystem? if you needed anthing AMIGA you could always run UAE.
Anyway, for my AMIGA, PFS is very quick and get's over the Gig problems for now. It's a shame it's hard to find now, I'm sure AMIGA users would be interested if it was available on AMINET. I hope AI (or whoever is setting the standards for AMIGA OS) make the new FFS to be as good as this FS seems to be.