There are many closed source applications that have been removed from the Google Play catalog for various reasons.
Often this reason is the cessation of further development and maintenance of the application.
Why don't these people make the code open to everyone if they don't need it anymore?
This could bring great benefits to all people, but everything that was once created simply disappears.
I have projects. Games that were in the google play store. One had hundreds of thousands of downloads. Then Google pulled it as I didn't maintain it. But, I have to pull artwork out, sound effects, etc that can not be included. And that's just time. I don't have much of that, that's due sure.
Maybe my idea is stupid, but what if ask for help? It may be possible to find programmers willing to help.