It's based on the Debian Free Software Guidelines (DFSG), which were adopted by the Debian Project to determine what software does, and does not, qualify to be incorporated into the core distribution. (There is a non-free section, it is not considered part of the core distribution.)
> Doesn’t open source mean the source is viewable/inspectable?
According to the OSI definition, you also need a right to modify the source and/or distribute patches.
> I don’t know any closed source apps that let you view the source.
A lot of them do, especially in the open-core space. THe model is called source-available.
If you're selling to enterprises and not gamers, that model makes sense. What stops large enterprises from pirating software is their own lawyers, not DRM.
This is why you can put a lot of strange provisions into enterprise software licenses, even if you have little to no way to enforce these provisions on a purely technical level.
Open source usually means that you are able to modify and redistribute the software in question freely. However between open and closed, there is another class - source-available software. From its wikipedia page:
> Any software is source-available in the broad sense as long its source code is distributed along with it, even if the user has no legal rights to use, share, modify or even compile it.
As I said above: Open-source is about what happens if the original author stops working on it. Having the code viewable/inspectable is a side effect of that - can't sustain a project if all you have are blobs. Famously, Richard Stallman started GNU because he wanted to fix a printer: "Particular incidents that motivated this include a case where an annoying printer couldn't be fixed because the source code was withheld from users." https://en.wikipedia.org/wiki/History_of_free_and_open-sourc...
