It would hold water if their solution was proprietary and closed source. But it isn’t, and anyone else, literally anyone, can take Proton and use it in their project for profit.
Even if they closed shop tomorrow, or even just gave up work on Proton itself, we’d all still reap the benefits at no cost to us.
When that store is run by a company that contributes massively to open source and works harder and puts more money into enabling alternate platforms for gaming than all other companies combined; ya, they have my loyalty.