syntax 1: %include(filename) syntax 2: %include(http://url)
DescriptionSyntax 1 "includes" a file name. It is reccomended that you included a full path or use the %fqppath() function. If you want the filename to be parsed, you should use %expand(%include(filename)).
Syntax 2 retrieves the contents of an http[s] url.
The Windows version supports the same options as "qweb" (http://www.q32.com/qweb.htm), since it shares the same source base. So you can specify a username, password, certificate file, and much more.
On Linux, for now, just use %exec(wget -O -...) or %exec(lynx -source ...).