Licensing is a complex problem and open source isn't some magical solution. It isn't the right model for every usecase out there and that's OK! Pay to play is sometimes the only fair and workable approach from a business perspective, but that doesn't make it open source. There's nothing wrong with that though!
Using terminology correctly is important. Timescale gets the terminology right and I appreciate that. (I also think it's awesome that they're releasing this product for free.)