Quote: " V2.0.20 fixed the LibPng issue (see changes here), but introduced other bugs to features that my apps rely on (namely GetImage), so I'm stuck."
This is
exactly where I've been stuck at in one of my WIPs for the very same reasons as you--since June when the last update was released. My game depends heavily on GetImage() for HUD generation and such so is completely broken with 2.0.20 (as I recall it also broke the ability to publish to iOS without some modification). Yet, I also depend on other features and fixes introduced in v2.20.0 to complete its development and resolve the libPNG vulnerability.
We know that Paul fixed the GetImage() command already on July 2, over two months ago. I've not touched AppGameKit since finding out about the GetImage() error of v2.0.20 but was hopeful we would get a quick bug fix update. It was originally claimed by TGC that updates would be fast and frequent, at least through the Steam distribution which makes it easy for developers to push out patches and updates. Clearly that has not been the case.