Getting error message, "You must install the legacy Java SE 6 runtime?" I'm getting the following error when trying to launch my application after upgrading Mac OSX:  



The more info says to go here and download this file.
Click "More Info…"
This will take you to this page.
Click "Download."
When it finishes downloading, run the installer.


tl;dr — literally just follow Apple's instructions and you should be set.