It's not normally in me, but I'd like to be a little forgiving toward users of GPG and similar infrastructure, particularly money-making BigCos. Open source, particularly reliance on open source by said MM BigCos, is relatively new.
It may not be financial ingratitude. It may be that we just haven't reached a sensible equilibrium between the two symbiotic ecosystems. At some point in the future, "due diligence" might commonly include identifying these sorts of tools, and their developers, and deciding either to not use the tool or to fund the tool's health.
By the time he searches for a new job, interviews, successfully gets a new job, stops contributing, and people finally NOTICE that he's abandoned the project: it's already too late.
You can offer him all the $5 donations in the world, but he has a full-time job now and has no reason to return to this life of "financial ingratitude".
I'm pretty sure we all would miss him working on it, either directly or indirectly, I think, as developers, we do a horrible job of assessing our blind spots when it comes to infrastructure.
You shouldn't always work just for money, but this is financial ingratitude.