Theses guides give some insight about how is developped Studio, so that some new comers can jump in at a limited cost (well, sort of...)
Studio is an Eclipse&tm; RCP application, which can also be loaded into an Eclipse&tm; instance. It's a set of plugins :
and various utility plugins.
You can check about what is needed to be able to start coding on the Developers' guide.
In any case, you need a Java JDK 7, Eclipse Luna-SR2, Maven 3.2.5, subversion 1.8.8.