It appears to me that the IIPA's own web site is hosted on the Open Source Apache web server. It's a little hard to tell because the Server header has been customised and there may be some sort of hardware loadbalancer in front of the server. Anyway the 404 page and the directory listings certainly look like Apache.

ACTA is a treaty on copyrights and trademarks, which are totally different than patents.

How can you possibly know what is contained in the ACTA treaty? While the actual contents remain secret (and they're likely to remain so until passed into law in the signatory countries) we have nothing to go on but leaked documents. Documents leaked already suggest the treaty aims to go well beyond simply protecting copyrights and trademarks. But of course all the countries involved in the negotiations already have laws to protect copyrights and trademarks so if the treaty didn't go beyond that there would be no reason for it to exist.