This is the home page for the SHOP, JSHOP, SHOP2, and JSHOP2. These automated-planning systems are distributed under an open-source license, and have been used in hundreds of projects worldwide. As of February 2013, there have been more than 20,000 downloads.
Announcement, June 2013:
Pyhop, a SHOP-like planner written in Python, is now available as open-source software at bitbucket.org. It's written in a way that should make it easier to learn and use, and easier to integrate with ordinary computer programs.
Go here to see earlier announcements.