This isn’t very well explained on the website, but most of the extensions on the extensions page that you’re getting this from are for older versions of Inform and won’t compile with the new one. Check the date–I think the up-to-date extensions will be April 2014 or later. You might also want to look at this thread.
Many up-to-date extensions that can’t be found in the Public Library are on an inform 7 repository on GitHub. You can find Inline Hyperlinks by Daniel Stelzer and Basic Hyperlinks by Emily Short there. Not sure if any of those mimcs Boselli’s extension in the way you want.