Hi unclecharlie, there's actually no spyware to be found on that site, so that seems to be a mistake in your school's web filter.

But here is a link to the forum post that has the measure distance plug-in:
http://moi3d.com/forum/index.php?webtag=MOI&msg=1661.7

To install the plugin, unzip the attachment and copy the 2 files (CustomDistance.htm and CustomDistance.js) into the \commands sub-folder underneath MoI's main installation folder.

Then to trigger it you need to set up a keyboard shortcut, to do that go to Options > Shortcut keys and push the Add button to add in a new entry at the top of the list. For the Key portion put in whatever key or key combination you would like to trigger it, and for the command part put in CustomDistance as the command name. Then when you push that key it will run that distance command.

- Michael