The available modules are the Mailbox API, Mailbox Store(the base and utility classes) and the different implementations we propose (Memory, JPA).
A module for tooling is also available.
The source can be checked out anonymously from GIT with the following command.
$ git clone http://git-wip-us.apache.org/repos/asf/james-project.git
$ cd mailbox
Everyone can access the GIT repository via HTTP, but Committers must checkout the GIT repository via HTTPS.
$ git clone https://git-wip-us.apache.org/repos/asf/james-project.git
$ cd mailbox
You can read a tutorial on how to build Apache James Server on http://james.apache.org/server/3/dev-build.html.
The GIT URLs and the project names must be adapted, but the requirements and process are the same and you can inspire from the build the Apache James Mailbox libraries.