[tsimionescu]

Only your third point makes any sense. For the other two, obviously the answer is yes, that's entirely reasonable. Businesses and government organizations use plenty of commercial tools that they have no way of designing or understanding on their own. Software is no different from hardware from this point of view.

A hospital doesn't have, and couldn't use even if it did, the blueprints for an MRI machine or an old-fashioned iron lung. And those machines are built by commercial companies and contain plenty of trade secrets.

If anything, using open-source software that you maintain yourself in critical infrastructure is the more bizarre practice from a historical or industry-level perspective. Even in software, things like Solaris, IBM OSs etc. are much more common than OSS. And even when using FOSS, a commercial distribution like RHEL is far more common than using your own Linux.

[prmoustache]

But do we really need "trade secrets" as a society?

[tsimionescu]

Even if companies were forced to publish every detail of their devices (which is the only way to not have trade secrets), any decently complex products products would still be black boxes to every company who is not specialized in creating them.

Even something like a fountain pen is used as a black box, I'm not even talking of anything truly complex. Even the buildings we work in are black boxes that we get from third parties, not to mention all the systems powering and heating or cooling them.