>     Since our web site runs MySQL, that means
> simutanuously 30-40 MySQL queries.

These are obviously not defaut httrack settings. HTTrack only opens four
connections simultaneously, generally "keep alive" connections (to reduce
additional handshake load), has a robots.txt built-in enabled by default, and
reduce the maximum download speed to 25KB/seconds. These limits are buil-in,
and setup *by default*.

You can change the settings, but it is the responsability of each user - and
most users won't touch them.

Unpolite users exists, but they can be unpolite with any other software.
Setting up such unreasonnable settings on a server using generated pages is a
clear abuse, and I can only recommend to blacklist its IP, or report the abuse
to its upstream provider.