I'm currently porting the ladder backend from PHP to Java.
There are a few reasons for me to do that:
With the root server in place, there's no need to stick to PHP anymore
Better flexibility to add new features (I'm much more comfortable in Java than PHP)
Hands on evaluation of my use case centric open source framework JUsecase
The new ladder backend is completely open source. Feel free to checkout the github repository and see the current progress.
Big thanks to the great people at Github, Travis CI and Coveralls! You're providing an amazing infrastructure to the open source community.