This is Lightning for PowerPC Mac OS X. (Unofficial build)
Lightning is already distributed with Tenfourbird. These xpi files are distributed for re-installation.
Mac OS X 10.4 or later (PowerPC)
Thunderbird compatible application (i.e. Tenfourbird) version 38.1.0 or later
v4.0.1 depends on dylibs in /opt/local/lib/libgcc directory. That may cause Tenfourbird crash if you haven't installed gcc in /opt/local. Use 188.8.131.52 instead. (Lighting distributed with Tenfourbird don't have this bug)
You can check integrity of files by RIPEMD160 or SHA512 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.