So I'm w/ Antoine that a dict would be better so that the other VMs can add whatever they want into that object (e.g. Jython could specify what JVM they are running against) without causing confusion as to what some index means to each VM. The mutability of it is not important IMO.

As for the other implementations using importlib, they all plan to with (hopefully) no direct modification, but whether they support bytecode I don't know (I think Jython has talked about it, but who knows).

And pertaining to whether this is useful outside of importlib, I suspect it is. We already have 'jython' as an "OS" type to work around some differences. Adding this attribute would more clearly delineate when another VM is being used that might require working around some difference without overloading os.name (e.g. PyPy implementing something differently in their 1.7 release of Python 2.7 but is subsequently fixed in their 1.8 release).