@Wazdakka, and others that might be wondering:
Visual Mode is a plug-in for Aleph One. It is NOT a plug-in for Weland.
In order to run Visual Mode you need to download: (1) Aleph One, (2) a Marathon Scenario.
Both of these are available for free online and easily discoverable via google.
-Put Aleph One into the Scenario folder.
-Put Visual Mode into the "Plug-Ins" folder within the Scenario folder.
-Replace the Map.scaA file with your own map. (Re-name your map to "Map.scaA"
-Launch Aleph One, start game. Texture!
Visual Mode is a plugin that allows you to texture maps in Aleph One. It supports almost all features of Forge's visual mode, plus OpenGL, multiple texture sets, and more. Requires Aleph One 1.7.