Would it change your opinion if he was paid for working on the software by the criminals?

Yes, it would change my armchair not-a-lawyer-but-i-play-one-online legal opinion. If there is evidence that he was (knowingly) hired to write the software by people who were planning to violate laws using the software, then it is not as much of an open-and-shut first amendment case (assuming they’re planning to extradite him to the US…).

It is currently unknown and given the nature of the software involved might never be known

Indeed. Which is why your assessment of his arrest should not be based on the assumption that that is what happened.