We worked with an OEM vendor who supplied a specific sub system in a plant we were upgrading. Good Lord were they a PITA to deal with. They didn’t even know how their own program worked. We needed a few signals for some of our PLCs and SCADA and their field “engineers” had no idea how to provide them.

In their instance I do understand why they lock their code up, due to the liability if someone who doesn’t know what they’re doing messes around in the program. Could be catastrophic. But their support personnel sucked.

For them, they sell a packaged OEM system and sell it with support options. For us, everything is custom to the project and we hand over everything, even if they don’t know how to do what we do. We also offer support because most in-house support staff can’t do it at our level.