The common sense definition for people who write code is the programmer definition that we've been using for as long as the term had existed. When you have no idea what you're talking about, and don't know what the terms used in software development actually mean, I can see how your definition might be entirely different. That's called ignorance, and you fix that with education.

> Calling anything without a formal license "closed source" is intellectually dishonest

No, it is not, because that is literally what closed source means. The source code is closed. You are not allowed to modify it. You are not allowed to copy it. It is not yours to use, copy or tinker with. It belongs exclusively to someone else and doing anything to it without explicit written permission opens you and probably your employer to litigation.