* You must upgrade to Config::JSON 1.1.0 or higher prior to upgrading.
    Due to a bug in CPAN you should type "force install Config::JSON" in
    order to upgrade to this version.
 * You must upgrade to the latest 7.3.x release before upgrading to
    7.4.0 or you will encounter fatal errors during the upgrade
    process.
 * WebGUI now requires the following additional perl modules to operate,
   and you should install them prior to upgrading:

    Config::JSON
    Text::CSV_XS
    Class::InsideOut
    HTML::TagCloud

Don't forget, always check the WebGUI/docs/gotcha.txt!
wg-fomATgwyDOTorg

WebGUI Runtime Environment (WRE) is a way to basically have WebGUI install all the dependencies in a neat little form factor.

What's the difference between WRE and the files above?
The files above basically point you to applying WebGUI to an existing web server, perl, database structure. WRE will attempt to install all the components for you on the OS of your choice.
It is important to note that you will be downloading the latest source after you download and install the WRE.
wg-fomATgwyDOTorg

How do I get old versions of WebGUI?

1) If you are at version less than 6.2.9, including 5.x, go to 6.2.11 (prepares for conversion from wobjects to assets.)
http://update.webgui.org/6.x.x/webgui-6.2.11-gamma.tar.gz
gotcha: http://www.plainblack.com/downloads/builds/6.2.11-gamma/WebGUI/docs/gotcha.txt
2) If you are at version less than 6.6, go to 6.6.5 (prepares for versioning)
http://update.webgui.org/6.x.x/webgui-6.6.5-gamma.tar.gz
gotcha http://www.plainblack.com/downloads/builds/6.6.5-gamma/WebGUI/docs/gotcha.txt
3) from 6.6.5, go to 6.8.10 (security fixes, versioning.)
http://update.webgui.org/6.x.x/webgui-6.8.10-gamma.tar.gz
gotcha http://www.plainblack.com/downloads/builds/6.8.10-gamma/WebGUI/docs/gotcha.txt
4) from 6.8.10, go to 7.1.3
http://update.webgui.org/7.x.x/webgui-7.1.3-stable.tar.gz
gotcha http://www.plainblack.com/downloads/builds/7.1.3-stable/WebGUI/docs/gotcha.txt
5) from 7.1.3, go to 7.2+ (or 7.3.22)
*** 7.3.9 must upgrade from 7.3.8, but 7.3.10+ will be able to upgrade from 7.1.3. ***

http://update.webgui.org/7.x.x/webgui-7.3.22-stable.tar.gz
gotcha http://www.plainblack.com/downloads/builds/7.3.22-stable/WebGUI/docs/gotcha.txt

7) from 7.3.22, go to 7.4.x
What this means: download ONLY the lowest version you need to upgrade each step. Install it per normal directions (including running the upgrade.pl! AND BACKING UP YOUR WEBGUI DIRECTORY), then grab the next "go to" version and install/upgrade it.
wg-fomATgwyDOTorg

    Cannot open config file:  at ../../lib/WebGUI/Config.pm line 348.
    Can't locate object method "http" via package "../.." at ../../lib/WebGUI/Session.pm line 370.
            Processing upgrade executable failed!

    The upgrade process failed and has stopped so you can either restore
    from backup, or attempt to fix the problem and continue.

    select webguiVersion from webguiVersion order by dateApplied desc, webguiVersion desc limit 1

    select webguiVersion from webguiVersion order by dateApplied desc, length(webguiVersion) desc, webguiVersion desc limit 1