Django-piston-app-engine is a project mainly written in Python, it's free.
A fork of django-piston modified to work on Google App Engine (specifically, app-engine-patch)
django-piston-app-engine is a Django style Python library for REST-style Web Services.
This library was forked from django-piston-app-engine on bitbucket, which appears stale. That django-piston-app-engine is a fork of the original project, django-piston. See [django-piston] (https://bitbucket.org/jespern/django-piston) for more information.