Java SE (Java Platform, Standard Edition)

Hi,

I'm getting confused by all those little JavaFX controls projects out there:

http://fxexperience.com/2013/05/announcing-controlsfx/

http://fxexperience.com/2012/10/announcing-the-javafx-ui-controls-sandbox/

http://jfxtras.org/


And then there's also http://www.javafxdata.org/

Why can't there be one?

I thought about contributing some code or ideas to such projects here and there, but never understood how it works with the source control systems. It seems some use Git, some use Mercurial. Unfortunately I don't have any experience with both and it always discourages me to begin with.
And there's also bitbucket and github. Never really worked with it. I also don't really understand what happens with my pull requests. Is there a super visor who would check my code and accept it or who else is responsible for the code quality?