Jython uses Java's native threads, there's no GIL.

Update: Jython 2.5 Easter egg

  >>> from __future__ import GIL
  Traceback (most recent call last):
  (no code object) at line 0
  File "", line 0
  SyntaxError: Never going to happen!

http://zyasoft.com/pythoneering/2008/06/realizing-jython-25....