If it was produced by konqueror, the it is a gzip archive:
file ONLamp.com\ --\ Customizing\ X\ Window\ An\ Introduction.war
ONLamp.com -- Customizing X Window An Introduction.war: gzip compressed data, was "", from Unix, last modified: Wed Nov 7 00:15:14 2007
You can extract the archive with tar: tar xvzf archive.war
The f option needs to precede the file argument. Tar is an old program, written before dashes were used for arguments, so they are optional.