> what have you to lose by putting up the paywall for support and fixes?
Your time, your energy and, given the jurisdiction this is likely to be in, your house and livelihood.
The guys and gals who are doing the maintenance are programmers who are already overstretched (that is the basic problem). Just to set up the tech mechanisms for a paywall may be something they've no experience in, so have to put time & effort into learning that (without any guarantee that the effort will have any payback; at least you can see your code working as soon as it is done). Then they are suddenly faced with all the brand new legal questions: are they now in any form of contract, having accepted the money? To whom and for what? What is their new tax situation? Have they missed something in setting this up? Do they need an accountant for this? Insurance? If some dev is done behind this paywall, does it stay forever behind it? Does the software licence even allow that to be feasible?
Are their new legal responsibilities going to clash with their current employment?
"But all those things are the natural habitat of a foundation and there are lots of software foundations around, it can't be that hard".
Great. But if one of those foundations wanted to take on this project they've had the chance to do so. And the "community" of freeloaders^^^^^^^^^^users who are complaining now have had all the time to help with that as well as all the time they've devoted to helping develop the codebase.
Unless... Are you going to leap into the breach and provide the devs with all the necessary to manage this simple paywall?