That's true that we don't let other web runtimes be used on FirefoxOS so far. There are good technical reasons for that, not just "mozilla is evil".
Doing while preserving security would mean that such a runtime would run sandboxed (in the same way we render web pages with gecko in sandboxed processes). For that to work, the sandboxed process need to delegate some functionality to the "main" trusted process, like network access. This is happening through an ipc protocol (we reused the one from chromium) but the messages exchanged are very much gecko specific currently, so a lot of work would be needed to turn that into a more generic ipc embedding interface.
I'm pretty sure that the folks working on Servo would be very happy to plug in their engine there ;)
'It's more work to be open' is an excuse we have heard for many years now from the likes of Microsoft. Often it was valid from a business point of view, but it's pretty amusing to see Mozilla using it now after years of PR campaigning about the importance of openness.
Perhaps you are starting to realise that running an open platform isn't as easy as you supposed, and a lot of Microsofts actions were not just "Microsoft is evil" either.
Doing while preserving security would mean that such a runtime would run sandboxed (in the same way we render web pages with gecko in sandboxed processes). For that to work, the sandboxed process need to delegate some functionality to the "main" trusted process, like network access. This is happening through an ipc protocol (we reused the one from chromium) but the messages exchanged are very much gecko specific currently, so a lot of work would be needed to turn that into a more generic ipc embedding interface.
I'm pretty sure that the folks working on Servo would be very happy to plug in their engine there ;)