why can't they implement a 'fake' GIL flag for those programs? so its backward compatible. (Yeah its probably a lot more work to write those extra modules/code paths... !)
It's not a "flag", really: it's a fundamental, implicit underlying assumption about the execution environment. The C extensions assume (roughly) that if they're executing, they can touch any part of the runtime without any synchronization whatsoever, because nobody else is executing (that's what GIL ensures).
