Why? how is competition better than collaboration?

webkit routinely gets breaking changes, it was never constrained because of compatibility concerns over non-standard features. Wouldn't having a load of developers in different environments, working on the same codebase actually accelerate innovation? Something could go from W3C/WHATWG draft to implementation in a matter of weeks, then we wouldn't have things like css3 gradients or flexbox syntax changing completely after years prefixed in the wild.

> it was never constrained because of compatibility concerns over non-standard features.

Seriously? You should go read the www-style archives or public-html archives or the relevant W3C bug databases sometimes for all the things the WebKit folks refused to implement (and still do) precisely because of such concerns.

> accelerate innovation?

Innovation and feature addition are not the same thing.

Please explain to me how building a rendering engine that scales well to 64 cores would be accelerated by starting with WebKit as a base, for example.

> Please explain to me how building a rendering engine that scales well to 64 cores would be accelerated by starting with WebKit as a base

I don't know enough about the webkit architecture to say anything, but I guess it wouldn't be any faster if it started with Presto.

While likely true, the value of multiple UAs as opposed to a monoculture is that it increases the likelihood that a revolutionary implementation that _can_ scare well to large number of cores would be able to get any traction at all instead of just being stillborn because it doesn't duplicate all the bugs of the monoculture.

So my point wasn't that one would build such a UA by starting with Presto. My point was that there are distinct advantages to competition over everyone using the same rendering engine.

What you're describing is "innovation" in its weakest form. It's basically incremental improvement, rather than real innovation.

Real innovation is far more drastic and disruptive. When it comes along, it often meets heavy resistance from those who are entrenched, especially when these people may not benefit from it. This is true even within open source projects. Unorthodox ideas will often be brutally crushed, even if the benefits they provide are immense.