Problem:

With both the installer and package downloaded from github i was getting:

>» Installing Cocos2D-v3.0.0 files
>» Installing Cocos2D-v3.0.0 templates
>» Building/Installing Cocos2D-v3.0.0 documentation, this may take a minute….
appledoc version: 2.2 (build 963)

Generation step 1/5 failed: GBHTMLOutputGenerator failed copying template files to output, aborting!
You don’t have permission to save the file “api-docs”.
You don’t have permission.
>» Cocos2D-v3.0.0 installation complete!

Solution:

It seams that the user which you are using to install Cocos 2d has to belong to the sudoers file.

Check Google for more details on how to do this.