This is quite simple, and should have happened before these companies decide to switch licenses because of Amazon. Each time Amazon decides to use an open source product, instead of doing it for free, they should contact the parent company and offer them a fee. There are many advantages of such an arrangement: a single version exists, the parent company has a stable source of income etc.
I might be mistaken, but this path was possibly chosen by Citus and Azure, and nobody seems to complain.