All downloads are in the files section under Sourceforge project page.
You can read also the full change log
If you want to get pop2owa source code check the Git page.
There is a stable branch and a developmental branch. Since version 1.0, pop2owa has adopted the same numbering scheme as the Linux kernel, which uses three numbers. The first number indicates a major version. Differences here usually mean that a lot of things have changed. The second number indicates if the release is stable (even number) or unstable (odd number). Finally the third number marks smaller differences between releases.