It's "Open source". That's the whole point of open sourcing code. As long as the lab attached the license provided it's good. This is completely different than copying code from private internal repositories.
You're missing the point / haven't read my other comment- in the context of academia plagiarism amounts to stealing. Sure, there's nothing that's legally preventing you from copying code and passing it off as your own so long as the license is preserved, but in academia this has political and sometimes economic ramifications.