Managed to finally get this running on El Capitan. Previously it would install and seemingly start running successfully, but then the Activation Wizard would come up with a blank window and it'd stay there forever. Getting past that ultimately required updating Internet Explorer (partial credit goes to Jack Phinney, as his mention of it here inspired me to give that a try). IE6 and service packs wouldn't install. IE7 didn't work; but it produced an endless array of "script error" dialogs when the Activation Wizard window appeared so it indicated I was on the right track. Installing IE8 ultimately did the trick, and it happily activated over the Internet for me and is now so far running just fine.
Hope this helps!