I know people die that way (GA). But someone is working for the companies that make insulin pumps and they are not as a rule equally motivated so I would expect them to do worse, not better.

And to the best of my knowledge none of the closed-loop people have died as a result of their work and they are very good at peer reviewing each others work to make sure it stays that way. And I'd trust my life to open source in such a setting long before I'd do it to closed source. At least I'd have a chance to see what the quality of the code is, which in the embedded space ranges from 'wow' all the way to 'no way they did that'.