RoboVM 0.0.14 has been released with initial Java on iOS 8 support
blog.robovm.org2 pointsby ntherning0 comments
sudo apt-get install build-essential g++-multilib openjdk-7-jdk
Then you also need to download an ICU data file and place it in /usr/share/icu: sudo mkdir -p /usr/share/icu
sudo sh -c 'curl "http://download.robovm.org/icudt48l.dat" > /usr/share/icu/icudt48l.dat'
From then on you should be able to follow the command line usage instructions to compile Linux x86 executables.
RoboVM on the other hand lets you use all the native iOS APIs from within Java and has a runtime library based on Android which limits you only to roughly the Java 6 APIs. As long as you structure your code properly RoboVM makes it possible to reuse large portions of your code between the Android and iOS versions of your app. So if you'd rather build an app that is truly native with a native UI and still want to be able to share code with Android RoboVM may be a better fit. And it's definitely not just for games even though libgdx+RoboVM is a killer combination.