Django ORM for desktop application

The Django people are sensible people with a philosophy of decoupling things. So yes, in theory you should be perfectly able to use Django's ORM in a standalone application.

Here's one guide I found: Django ORM as a standalone component.

Yes it is. The Commonsense Computing Project at the MIT media lab does that for ConceptNet, a semantic network. You can get the source here:

I would suggest using SQLAlchemy and a declarative layer on top of it such as Elixir if you prefer a Django-like syntax.