Google Chrome no longer allows the installation of extensions from sources other than the official Google extensions page, all of which are vetted and curated by the company. Sounds familiar. Gary Mark of BrowserFame writes:
Chrome team explains the reason for this policy change, “To help keep you safe on the web, we have started analyzing every extension that is uploaded to the Web Store and take down those we recognize to be malicious. Unfortunately, we don’t have the ability to take down malicious items promoted on other websites […]”. This change has affected all third-party extension galleries (including those launched even before Google’s Web Store) and UserScripts.org. I am specially mentioning UserScripts.org because this site is the biggest repository of userscripts.
Sounds open to me.