July 2016

axel is a command-line utility, similar to curl and wget. In fact, axel can be substituted for wget for the most part, sans the additional options it provides (and vice-versa).

It can be installed on OS X through homebrew.

brew install axel

An anecdotal example seen in the screenshots below. axel downloads a 11.38 GB file at a rate of 56.46 MB/sec, compared to 27.3 MB/sec with wget. Of course, depending on numerous different factors, there may be little difference between the comparative download speeds, or even the opposite pattern.

axel download rate example

wget download rate example

It certainly does not hurt to have both tools in your toolkit! See also details of package axel on debian.org.

  1. Firstly, proceed with the following instructions at your own risk. I assume no responsibility for lost data or broken using experiences as a result of this workaround. In general, it is unlikely that any irrevisible changes will happen as a result of importing an extension that has not been tested for your installed version of Firefox/Thunderbird, as you will most likely be able to just uninstall it if it does not work as desired.
  2. Download the *.xpi file using a browser other than Firefox. This seemed to be the only way that I was able to actually “Download Anyway” an extension.
  3. Using an archive manager, open the downloaded *.xpi file. I used Engrampa which is part of the MATE desktop, but that by no means is exclusive. Inside this archive, you’ll want to modify a file named install.rdf:
    <?xml version="1.0"?>
    <RDF xmlns="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
    xmlns:em="http://www.mozilla.org/2004/em-rdf#">
    
    <Description about="urn:mozilla:install-manifest">
    <em:type>4</em:type>
    <em:id>{77d2ed30-4cd2-11e0-b8af-0800200c9a66}</em:id>
    <em:version>14.0</em:version>
    
    <!-- Target Application this extension can install into,
    with minimum and maximum supported versions. -->
    
    <em:targetApplication>
    <Description>
    <!-- Firefox's UUID // DO NOT CHANGE-->
    <em:id>{ec8030f7-c20a-464f-9b0e-13a3a9e97384}</em:id>
    <!-- End Firefox's UUID // -->
    <em:minVersion>44.0a1</em:minVersion>
    <em:maxVersion>45.*</em:maxVersion>
    </Description>
    </em:targetApplication>
    <em:unpack>true</em:unpack>
    
    <!-- Front End MetaData -->
    <!-- My_Theme -->
    <em:name>FT DeepDark</em:name>
    <em:description>Smooth dark theme for Firefox</em:description>
    <em:creator>Stefano</em:creator>
    <em:contributor>Stefano</em:contributor>
    <em:homepageURL>http://www.stefrosselli.com</em:homepageURL>
    
    <em:internalName>ftdeepdark</em:internalName>
    </Description>
    
    </RDF>
    

    Bump up the version of em:maxVersion to be inclusive of the version of Firefox/Thunderbird you are using, save the file and update the archive with the updated version of that file, and now manually import the extension as a file.

    In many cases, such as themes, this has worked for me well with the Nightly channels of Firefox and Thunderbird (50.0a). Below is a screenshot of the elementary Thunderbird theme installed successfully on Daily (50.0a).

elementary Thunderbird theme on Daily