CS2J is the most advanced C# to Java conversion tool available today.
 
- CS2J produces good looking, maintainable Java software from your C#
  source code.
- It uses a powerful, extensible template system to translate .NET
  Framework and 3rd party library calls.
- It is a command-line tool which can be easily incorporated into your
  existing development workflow.
- And it is completely Open Source!

The CS2J source distribution has two components:

- CSharpTranslator:
     This builds the cs2j.exe executable.  This executable runs
     directly under Windows and under Mono on other platforms
     (http://www.mono-project.com/Main_Page).

     This work is licensed under the MIT / X Window System License
     (http://opensource.org/licenses/mit-license.php). 

     With this licensing then the produced Java code should be
     completely unencumbered and you can do what you want with it.

- CS2JLibrary: 

     This contains the XML translation files that direct cs2j to
     translate .Net framework calls into appropriate Java code, and
     the CS2JLibrary Java support library that translated applications
     include.

     This work is licensed under the Apache License, Version 2.0
     (http://www.apache.org/licenses/LICENSE-2.0).