Is RTEMS an active project? They should file a copyright complaint and have the libogc repo taken down if this is true. If it were me, I'd lawyer up and throw the book at them. LibOGC accepts donations via Patreon, which means -- if the allegations are true -- they're profiting off stolen code. RTEMS could and should sue for damages. This isn't the first time I've seen an open source project stolen by someone trying…
Litigation is expensive.
Yeah, hobbies can be expensive and sure litigation could be someone’s hobby…nothing wrong with that and maybe worth having lawyers on retainer if that’s your jam.
But in this case, there’s probably not a business case…and being a civil matter, there’s no book-‘em Danoh book to throw. Just normal squeezing blood from turnips…which again, might be someone’s hobby at least in theory.