Oh come on Tom. Making a great, free toolkit utterly decimated the competition. Just completely destroyed any funding for a competitor. And I should know.
I believe that you believe this is well intentioned, but it had a very negative impact on open source geospatial software development. Again, I SHOULD KNOW.
Mapbox is doing what is good for Mapbox. It's a company. But let's not pretend this change is good for anyone but Mapbox.
We make a competitor to MapboxGL for mobile called WhirlyGlobe-Maply (https://mousebird.github.io/WhirlyGlobe/).
It supports vector tiles & Mapbox style sheets, works on Android and iOS, even supporting Metal on iOS. Indirect mode in Metal, actually, which is no mean feat.
WhirlyGlobe/Maply has been around a long time. It actually predates MapboxGL and it's used in popular apps like Dark Sky, as well as a ton of aviation apps and a not a few GIS apps.
Engineers like to write their own, so we're going to hear from a ton of random projects here. And hey, more power to 'em.
But you're looking for a fast, open source mobile map toolkit that's going to be around next week? It us.