Wow, that is spectacular. You pay for the board license and they cannot even give you a working copy of the install script. That is like selling a television with only one input. Eventually you are going to need more.
all of the add ons for IPB are created by either third party organizations, or just regular people. such as the download system neocodex uses. it wasn't made by IPS, but by individual coders at websites such as invisionize.com, or at ipbmods.net. sometimes the add ons are so good, IPB integrates them into the core build.
oops marine already answered