For my little framework Pyxer I would like to to be able to use the Google AppEngine datastores also outside of AppEngine projects, because I\'m now used to this ORM pattern
There is also the Remote API which the bulkloader tool uses to upload or download data into/from the Datastore.
Maybe it could be used to have applications which are not hosted on AppEngine to still use the Datastore there.
You might also want to look at AppScale, which is "a platform that allows users to deploy and host their own Google App Engine applications".
It's probably overkill for your purposes, but definitely something to look into.
Nick Johnson, from the app engine team himself, has a blog posting listing some of the alternatives, including his BDBdatastore.
However, that assumes you want to use exactly the same ORM that you use now in app engine. There are tons of ORM options in general out there, though I am not familiar with the state of the art in Python. This question does seem to address the issue though.