Yes, I'm not funded by the millions (like Khan Academy, the org that created/sponsored Katex) so I would hate to see all my hard work get copy/pasted by a company, rebranded as their own and sold to the public in a private manner.
> I don't want to think about licenses at all in my life
If you don't want to think about licenses ever it's just a one-time payment of $19, that's exactly why I dual-licensed it; follow the license, or pay $19 to not deal with the license.
> That makes me less interested, really
That's okay, if you don't think it's a library worth $19 (or following the license), it means it doesn't provide enough value for you to be worth of your money. For the average developer in the world that's less than 1h of their time though, so if you think that my library will save you 1h vs others, or vs doing it by hand, then it's "worth it". Many developers think all the tools should be MIT, and that is okay, but I don't share that ideology.