I reckon you're asking a meaningless question. It's like asking "Is front wheel drive a valid business model?" Open source is not a business model at all, so

I reckon you're asking a meaningless question. It's like asking "Is front wheel drive a valid business model?" Open source is not a business model at all, so it's cannot be either valid or invalid. Some companies build successful business models that use open source software (like Redhat). Some companies struggle with some of the difficulties of competitors being allowed to use their open source software (like Redis/MongoDB). And guessing based off your username and one of today's front page new items, you might be asking about companies like Wassmer - which seem to be struggling with the idea that to have a "business model" you need to have a thing people/companies will pay you money for.