Since a few minutes GridFX is official part of JFXtras. I will remove all sources from the old github repository in a little while. Thanks to everyone who helped me to go this way. So if you want to try GridFX just check out JFXtras here or wait for the next release.
[...] part two of his series of posts on custom UI controls in JavaFX. He also has announced that GridFX is now part of JFXtras (which is great news), and that GridFX is now styleable via CSS with custom CSS [...]