I appreciate that it is a bit vague - we've decided to draw the line at patches, for which you'd still need the original to run them. Similarly, JJ2+ technically violates JJ2's EULA, but Epic is okay with that being distributed.

I certainly agree that it's worth sharing, though, so thank you for posting about this here. Is the person that gave you permission to do so one of JJ3's developers? That'd imply that it would at least be okay to distribute the design documents, et cetera, which don't contain engine code. I've sent a message to the original developers myself to check whether they'd be okay with linking those, since they're probably the biggest find in this release and really interesting to read.