Own them all! Love his work, they are among my favourite games. But Action Tales isn't open and I did FU long before Action Tales, so this is where the material comes from.
Having spoken to Nathan on a few occasions, including recording an interview with him for a local con, I don't think he would mind you putting out a free PDF of optional rules for Action Tales.
I imagine if you contacted him using the form here, he'd even give you express permission.