Probably the biggest reason none of the alternative Python implementations have taken off is a lack of compatibility with native libraries. Pypy is arguably fas

Probably the biggest reason none of the alternative Python implementations have taken off is a lack of compatibility with native libraries. Pypy is arguably faster and easier to operate than Jython, but it's unpopular for essentially the same reason: compatibility. I have a hard time accepting that py3k is what suffocated Jython. Pypy, pyston, and most other modern alternative interpreters all have some amount of py3k compatibility. The fact that there hasn't been investment in Jython to bring the same improvements suggests other causes for Jython's demise.