Regulation could go a long way, e.g. tax incentives for open source development or using open standard/platforms. Imagine giving developers or companies lower tax rates on profits from open source products, e.g. for resulting donation income.
That way they could operate cheaper and could pass the savings in tax on to users or investors. For clients this would be nice too, they could reduce the risk of being locked in when choosing a provider and shouldn’t care as long as it’s not their core business.
The challenge would be preventing misuse and how to get countries to give away tax income that other countries might use.
The behemoths are already based upon open source tech and have contributed to it. But what they make on top of it neither has its "schema" (software sufficient to fork your own) open nor the instances accessible or communicatable. The same way that installing Linux doesn't mean I can access your files or configurations on top of them. The way I see it that is a price of open source software that you can't control how others use it in exchange for not being controlled.
Open standards as positive externalities would be a rational reason for tax discounts even if the value of it varies greatly - although good for repairs few would care for a specific printer model's firmware as it is so specific in its domain.
That way they could operate cheaper and could pass the savings in tax on to users or investors. For clients this would be nice too, they could reduce the risk of being locked in when choosing a provider and shouldn’t care as long as it’s not their core business.
The challenge would be preventing misuse and how to get countries to give away tax income that other countries might use.