What you're talking about is "source-available." I.e. being able to read source code but not having licensing rights to redistribute or make changes.
"Open-source" means that being able to modify and distribute changes is built into the license of the code.
For example, Minecraft Java is source-available in that decompiling Java bytecode is trivial - enough so that tools exist which can easily generate a source code dump. However, actually distributing that source code dump is technically illegal and falls under piracy, so it isn't open source.
Edit: I didn't see your edit, this comment is kind of pointless, oh well


It's an Android app patcher that removes ads and adds some other quality of life patches. Primarily for YouTube but it supports several other apps as well.
On YouTube it also adds things like integrated SponsorBlock, extrapolating dislikes, actual resolution buttons, and the option to disable shorts.