Looks like @Sidane may be the user who runs/works on that website you linked to (the website is linked to on his profile). He may be worth contacting.
Also the add-on appears to have references to EWRblock_TabbedContent.css in the code - this is likely from the XenPorta add-on, the author of that add-on is @Jaxel he may be able to provide some insight as to how that is achieved.
The add-on used is XenPorta however it has been heavily customised by the owner, there are many custom mods RedCafe are using that have been developed by the owner.
You could probably accomplish something very similar with [bd] Widget Framework using Widget Groups (they create the tabs, and have different widgets on each one. At that point it's just a matter of changing up some CSS