They weren't studying the community, they were studying the patching process used by that community, which a normal IRB would and should consider to be research on a process and therefore not human Research. That's how they presented it to the IRB so it got passed even if what they were claiming was clearly bullshit.

This research had the potential to cause harm to people despite not being human research and was therefore ethically questionable at best. Because they presented the research as not posing potential harm to real people that means they lied to the IRB, which is grounds for dismissal and potential discreditation of all participants (their post-graduate degrees could be revoked by their original school or simply treated as invalid by the educational community at large). Discreditation is unlikely, but loss of tenure for something like this is not out of the question, which would effectively end the professor's career anyway.

In my experience in university research, the correct portrayal of the ethical impact is the burden of the researchers unfortunately, and the most plausible explanation in my view given their lack of documentation of the request for IRB exemption would be that they misconstrued the impact of the research.

It seems very possible to me that an IRB wouldn't have accepted their proposed methodology if they hadn't received an exemption.