People often use the OSI’s Open Source Definition when using the term “open source”. One of its criteria says “The license must allow modifications and derived works” which this license does not allow.

It’s a twitch meme

You might want to check out microMathematics Plus. I last used it a few years ago. I remember being impressed by it, but thought it was way overkill for something I’d need on my phone.

I wouldn’t go to such a shop. Most people wouldn’t.

Idk, it sounded a lot like what Amazon is these days