OER are not able to generate revenue so they can not be a business model

OER, same as open source, can create revenue in many different and successful ways. From services like search engines or platforms built around resources, selling custom versions or providing implementations. From a business perspective OER projects are more like startups

OER are not sustainable

Discussing sustainability of OER is a rather complex issue and depends on many factors. It is very strongly linked to the business approach and can be guaranteed by choosing (adequate) business models that generate revenue. The sustainability becomes a priority