I've burned myself twice on this approach. Shortly after I/we started supporting them they changed their license terms. Of course since we were now paying customers we could still use it, but a significant reasons why I advocated for that software in the first place was because it was open source, and now I feel cheated and the advice I gave the company I worked for at that point turned out to be less valuable.
I do sometimes feel that once one get the taste for that sweet sweet recurring revenue it is hard to not start optimizing for it.
For completeness; it has also worked beautifully at least once.
And I guess I'll probably argue again for supporting open source.
But maybe I'll be a little more careful and try to ensure they can't pull these kinds of tricks on me (if a project accepts code contributions and doesn't have a CLA, it will be hard for them to pull such a bait and switch).
Finance is a significant obstacle to this goal. Multiple times I have been told, “There is a budget surplus-does anyone have any nice-to-haves we should purchase?” More than once, I have suggested (modest) donations towards open source project X that enables us to operate. Not once have I succeeded.
Not a real charity. Not a real purchase. Good will towards something already free does not make a compelling business case up the chain of command.
I'm playing devil's advocate there: I do actually think it is the right thing to do to pay the author. But I don't think your argument would work with a manager.
If you want $$$ from enterprise, offer them cost saving or money making tech and charge for it. It can be built on top of your OSS, in fact this is a great way to get in touch with the companies... But don't rely on charity. In the companies I worked for paying for something you can get for free is simply not done, ever.