Most probably SQL Developer application doesn't support high DPI, and Windows scales it up. This blog post provides more detail: http://blogs.msdn.com/b/patricka/ar...ication-look-fuzzy-and-have-clipped-text.aspx
It may look a tad better if you disable retina support for the entire VM, but you'll sacrifice display sharpness in other apps. There isn't much else you can do besides contacting SQL Developer support.