Tenfourbird ist inoffiziell Build von Mozilla Thunderbird für PowerPC-basierten Mac OS X.
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.