The Eclipse projects are all stored in the Eclipse Foundation CVS servers. Using the source is a great way to debug your code and to figure out how to do new things.
Unfortunately in a large software project like BIRT, it can be difficult which projects and versions are required for a particular build. So what is the best way to get the source for a particular build.
Okay, I know the answer to this one...
Eclipse has a feature named Team Project Sets which allows you to define a collection of projects, stored in various version control systems that can be downloaded as a package. I have published a collection of team project set files that can be used to get the BIRT source. The files are stored in a Subversion repository here
I have a short article with a bit more detail on the BirtWorld blog.