Django-cms with non-django-based project
No, it's not possible. 
django CMS is a standard Django application, that requires a standard kind of Django environment. It can't do anything except as part of a Django project.
There's nothing to stop you configuring your web server so that some requests (by URL) go to the Django project while the others are handled by the Java backend, but this isn't integration, it's simply some form of wholly independent co-existence.
I have a project with a Java backend and Angular-based frontend and I'd like to utilize Django-cms. Is this possible to do with a non-Django project? I've been looking over the documentation, but I can't find an explicit 'yes' or 'no'. I can't wrap my head around how I'd integrate, what seem to me, two very different projects.