[Plasmoid]

Words mean things. If you say open source, people are going to expect that your license is going to follow the existing expectations set by OSI.

Think about this as setting expectations. You can avoid all the controversy by saying that your software has a generous 'source-available' license. People will know they don't get all the freedoms, and that might be ok, but people won't get upset that you misled them.

[Pannoniae]

Fair enough, you are entirely right. But wouldn't that draw a different complaint about "why isn't this open source then if you published the code anyway"? I don't have an example right now but I've seen several projects where it's been a huge source of controversy that they've made it source-available but didn't use any FOSS licence for it.