Eclipse Acceleo is an open source code generator implementing the OMG's MOF Model to Text Language (MTL) standard that uses any EMF based models (UML, SysML, domain specific models...) to generate any kind of code (Java, C, PHP...) while keeping the traceability of the generated text.
You do not need to be an expert to start using the plug-ins and create your first code generator : using the provided example projects and the powerful completion feature of the Acceleo editor, it is very easy to get started and understand the basic principles.
You can get a quick glance at Acceleo with the demonstration that was presented at the Eclipse Modeling Runaway 2010.
More information is available on the wiki page for Acceleo.
The Eclipse Acceleo project was started 4 years ago. Over the years, it steadily grew from its first stable release up to its 2.x versions. Yet, the team has been more and more convinced that the future of code generation lied in the OMG MTL specification, and that it was the way to go for the project. The reference implementation we provide within the Eclipse M2T project, Acceleo 3.0, combines nice tooling, simple syntax and efficient code generation with all the pragmatism we had with the 2.x stream.