I think that is a problem many open source programs have, and could improve. A lot of GUI based programs should think of implementing parts of it as a library

I think that is a problem many open source programs have, and could improve. A lot of GUI based programs should think of implementing parts of it as a library others can use. I remember early Git implementations in IDEs where they just ran git commands in the background and parsed the command line output. Imagine if the same had been done with SQLite, would it still be as popular today? I don't have much experience with creating desktop software, but it seems to me that separating the GUI from the "engine" would bring other benefits too. I have often looked at OSS and wanted to use parts of it myself. An email client might have a really good mail parser that handles encoding, attachments etc. But decoupling it from the rest of the program would take too much time.