Our latest official releases are always available at https://github.com/omf2097/openomf/releases. The official releases are always tested to work, but may be heavily out of date.
There are unofficial windows and linux binaries available at http://katajakasa.fi/projects/openomf/packages/. These are updated every now and then, and may or may not work. Use with caution!
We also have (sometimes) updated macosx package available at http://hijacked.us/~andrew/openomf-0.6.6.dmg.
The sources are available at our main repository at http://www.github.com/omf2097/openomf/ and as downloadable archives (master branch) from the links below:
Installation instructions are available in our main code repository, at https://github.com/omf2097/openomf/blob/master/INSTALL.md.