Tenfourbird is unofficial build of Mozilla Thunderbird for PowerPC based Mac OS X.
Tenfourbird uses changesets of TenFourFox.
Latest version is 38.9.0.
You can check integrity of files by SHA1 hashes. It also signed by OpenPGP key of t_mrc-ct[at]users.sourceforge.jp. The public key could get from here or OpenPGP Keysever.
Some langpacks (de, en-GB, es-ES, fr, it, ja-JP-mac) for Tenfourbird are updated.
Other langpacks (nl, pt-BR, pl, ru) are not updated since 17.0.