So... for instance, when you try to star a project, it will follow a link (404) instead of toggling the star.

I tried enabling the github mode, but it sees to be focused on letting the shortcuts work (which, by the
way don't work correctly (e.g. the useful t shortcut does not work)).

See if keykill-mode resolves this issue for you.

Tried keykill-mode and it still does not work. I'm running conkeror on OSX Lion, if that matters.
  
So, correct me if I'm wrong, but Conkeror uses the same redering engine than Firefox, as well as its
javascript engine... so why do sites look different than in firefox? and why some javascript stuff does
not work?

> why do sites look different than in firefox?

This is usually due to websites serving different content based on your user-agent string.

I couldn't reproduce the problem with 'starring' a project.  Tried both
with mouse and with the keyboard ('follow' command), and with both
Conkeror's normal user-agent string, and a Firefox ua-string.  Tested with
current Conkeror HEAD on XULRunner 15.

To be clear, the 'star' button that I tested was the one on the upper
right of a project page, between 'fork' and 'watch'.

I was using XULrunner 1.9.2

I tried installing conkeror using the latest version (25) and it does not work (xulrunner crashes); I
tried using version 15, and it didn't work either (it complains about not finding libmozglue.dylib).

Then, I followed the Installation based on Firefox and it's working fine. The rendering issues I had
noted are gone, and the starring works perfect.

Just found something that is does not work: when you are on github and press g to jump to another url, it
does nothing. I tried without using any config; using github mode; using key-kill; and it just doesn't
work. I can live with this, so feel free to close this issue. Or if you want, we can investigate this
further.

Hmm, unable to reproduce that one here, either.