If it was decompiled, that's not really reverse engineering though. So I'm not confident that the DMCA carve out would apply here.

Decompilation is very much part of reverse engineering. The two are not the same, but disassembling and decompiling code are extremely common techniques used to reverse engineer a program, algorithm, or protocol.

That's clearly "hacker true". I wonder if it's "lawyer true" as well? It could very well not be.