These are Debian/Ubuntu package repositories. New packages are built nightly (if new changes are available). Pick the branch + version + architecture you want and add it to your sources.list, similar to this:

deb http://code.bitlbee.org/debian/devel/testing/amd64/ ./

Packages are available for i386/amd64 machines, but also for ARM (armel). The latter are built for a smaller selection of distro versions (more or less two Debian and two Ubuntu versions) due to capacity constraints.

You can add the signing key (signed by E3304051, wilmer@gaast.net, which has a pretty reasonable trust path) to your apt configs by copy-pasting the following into a shell window:

sudo apt-key add - << EOF
-----BEGIN PGP PUBLIC KEY BLOCK-----
Version: GnuPG v1.4.9 (GNU/Linux)   
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=Ktl0
-----END PGP PUBLIC KEY BLOCK-----
EOF