Xs is a cleanly-designed shell with functional programming. It is based off
the source-code for the es project, which was in the public domain.
Currently, the changes in xs can also be considered to be in the public domain.
Most of the xs source code remains untouched from es.
The primary authors of that shell can be found in that source code,
currently located at: ftp://ftp.sys.utoronto.ca/pub/es/. Modifications
since es-0.9-beta1 are all parts of xs and have been written by
Frederic Koehler.
