The latest version is birdfont-0.31.tar.gz. Source code for all versions can be downloaded from the release directory.
A Ubuntu package is available at launchpad.
A package is available for OpenBSD in graphics/birdfont.
You can download BirdFont packages under thre different licenses.
- Source code package under the GNU GPL.
- Freeware version for SIL fonts.
- Commercial version for proprietary fonts.
I recommend that you download the source code package. The commercial version can be downloaded if you donate 1 US$ or more.