[bdon]

Some CDNs handle range requests; the purpose of introducing Lambda/Workers here is to transform normal Z/X/Y URLs into range requests, so you can use PMTiles with any client like MapLibre Native or legacy code without loading a plugin.

Protomaps actually has its own vector renderer different from Mapbox GL or MapLibre at https://github.com/protomaps/protomaps.js . It does use a handful of low-level Mapbox JavaScript libraries, but otherwise was consciously developed to be 100% separate from existing Mapbox rendering and styling code, and has an objectively inferior (Leaflet) user experience.

In practice, most serious uses of Protomaps are now using MapLibre GL, so there will be more focus going on that in the project going forward.