LibTar is a unit in the FCL that creates and extracts .TAR archives.
There are two demos in the fcl/tests directory: tarmakercons.pas and tarmakerconsgzip.pas. The latter demonstrates making .tar.gz files.
This package was kindly relicensed for FPC licensing conditions + MPL (so called dual license) by Stefan Heymann, www.destructor.de. The original license was "postcardware" like, and Stefan has stated that he still likes to receive postcards from users, it is just not mandatory. See above URL for the address data.