I believe unedditreddit was removed due to trademark issues, but I could be wrong. As this extension does not have any of Yale's trademarks within and (demonstrably, based on source) does not impact the site, Yale should not have a leg to stand on.

But your point about doing it in Firefox is a very good one. Firefox's extension addons site is much more democratic. And side-loading extensions within Firefox outside of addons.mozilla.org is something even an inexperienced user can accomplish.