I'm with you on "not open source", but I don't think "proprietary" works as the opposite of "open source" here.

The dictionary definition of "proprietary" tends towards "one that possesses, owns, or holds exclusive right to something" - that doesn't quite fit here, because models licensed under OpenRAIL aren't exclusively restricted to their owners.

They have terms of how they can used that are more restrictive than open source licenses, but they don't enforce "exclusive" usage by their owners.