If you want to become a millionaire make your software product commercial. If you want it to be open-source, keep it that way forever and don't start complaining "Oh, I really want to be a millionaire but I'm not because all these people are using my code for free! Now all you millions of people who are using my code should pay me from now on!"
I believe charging for software after you've gained a user base in the millions is akin to a rug-pull scam. I even believe that criminal liability comes into play here.
It's a good thing the .NET Foundation expels all the projects that change their licensing to commercial.