Earlier quoted context omitted.
I don't even see any moral issues here. Is there any reason to believe the original author acted in bad faith? If you sell your used car and it gets used to rob a bank, did you act immorally?
If you run a business where you have convinced people to give you access to their house to do some chore and you sell your business and your copy of their keys to a criminal it could be morally problematic. A car is merely a fungible vehicle the customer would have been no better or worse off had the robber been driving a different car. This would be an apt analogy for just giving / selling a code base. Had it been d…
This implies the seller _knows_ the one they are handing over the keys to is indeed a criminal. In that case it is certainly morally problematic.
I see your point but I still think calling the maintainer's behaviour immoral is going a bit too far. Perhaps careless. Or maybe naive. But not more than that.