Mojo is one of the applications that runs on the Openmoko Phones. For a list of all applications, visit Applications
Mojo is an experimental mail client written in Java SE and SWT. It runs on top of Jalimo.
There are two tarballs available - for Openmoko and for x86 Desktop Linux. All instructions are in those archives (basically you just have to run the installation script).
Next step is an IPK package. But you don't have to worry, the bash script in current installation is user friendly enough ;).
Because project space on Openmoko Projects have some unresolved issues with my svn account, I currently keep source code on my private svn. As soon as we get svn.openmoko working, I will place all the source code there. Until that you can download tar file with source code and Maven2 structure, including pom.xml.
The code has detailed comments, but they are in CZ. With release on the svn I will place there version with translated comments in EN.
You can use the mail list or forums on the project page https://projects.openmoko.org/projects/mojo/.