Does the amount of labor that was provided by a community make a difference? What if it was minimal? Where do you draw the line (any piece of code accepted, or a "large portion" of code)?

I didn't downvote you, but I suspect combining PRs with issues is what most people have an issue with. Issues obviously help to improve software, but only through the fixing or writing of new code.

Maybe I'm in the minority, but I also think that if it were a requirement to never close source your project after it's already been open sourced, we'd have far fewer projects available that are open source. Often a project is created on a company's dime, and open source, to draw attention to the developer skills and ability to solve a problem. If the code was legally disallowed to be close sourced in the future, we might see far less code available universally. A working repository of code is potentially a reference for another developer to learn something new. I don't have any examples, but I know for a fact that I've read code that had been open source, and later close sourced, and learned something from the open source version (even if it was out of date for the latest libraries/platform).