[HTTPS-Everywhere] "Author not verified" while trying to install "HTTPS Everywhere 2.2" (Firefox 14.0.1, Mac OS X 10.6.8)

[Tagglez Tagglez]

Hello,
I am trying to install "HTTPS Everywhere" on a fresh install of Firefox 14.0.1, using Mac OS X 10.6.8.
I went to the website 

https://www.eff.org/https-everywhere
and
 clicked on the "Install in Firefox - version 2.2 stable" icon on the 
page.  Firefox responds by showing me a message "Firefox prevented this 
site (www.eff.org)
 from asking you install software on your computer" and an "Allow" 
button.  When I click on the "Allow" button, and the extension has 
finished downloading, I get a warning dialog box about installing 
downloads from trusted authors, and the caption "You have asked to 
install the following items", followed by a list
 box with the item "HTTPS Everywhere (Author not verified)".
Should
 I go ahead and allow the installation to complete even with the "Author
 not verified" message, or should I assume that the extension Firefox 
downloaded is not authentic?  Having been hit by a malicious Trojan 
before (when I was tricked into downloading a so-called "Flash plug-in 
update" for Firefox many years ago, which has kept me away from Firefox 
until now), I am quite cautious  these days.  Are there alternative ways
 of confirming the authenticity of the downloaded "Https Everywhere" 
extension along the lines of an MD5 check-sum or
 something?

Thanks in advance.
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