Python finally succeeds in cross-platform areas where Java has been failing...

[Roy Smith]

How much of Python's cross-platform advantage over Java is due to the 
single source of the Python interpreter and how much is due to the 
language itself?

There's certainly nothing (that I'm aware of, other than time, money, 
and skill) to stop me from writing my own Python interpreter, making 
some subtle changes in behavior (either intentionally or by accident) 
and promoting it in the field.  If I could convince enough people to 
install it, we'd suddenly have a cross-platform crisis in the Python 
world.

This is really all that's happened in the Java world.  The above 
scenario describes what Microsoft did to Java. The only difference 
between me doing my own Python and Microsoft doing their own Java is 
that Microsoft has the resources and desire to pull it off.

What would happen if Microsoft saw Python as a threat and decided to 
kill it by shipping their own incompatable Python interpreter with 
Windows?  Would we have any defense?