I'm sure they can find outsiders happy to review code contributions. Any decently-run OSS project would already do this, after all, so it wouldn't be hard to just contact them and find a person already active in that organization willing to do the review and communicate back to the prison, assuming it's a project that really would like some extra full-time help for the next ~50-75 years (not all might, but some definitely would).

What other "more pressing matters" could there be anyway? Making license plates? This guy is smart and experienced with software development. It would be a waste for him to do something as mundane as making license plates or digging ditches (I don't even think they use prisoners for that these days).