2.0.3 of invision board is a paid only version. Unless you are talking about the trial version with limitations.
Yes, you can't buy one copy and use it on multiple boards, the script checks back with IPB on the validity of your license that is in turn tied to your domain.
Then there is the Nullified version, but this isn't exactly some fly by night site with 10 active members. Nullified script are ok for small sites or personal sites, but unless you want a lawsuit, don't even bother running that.
This current version is fine, just needs a lil bit of patches to get over the sql injection issues. 3 to 4 files at most.
And for crying out loud, for the sake of all genuine hackers out there, stop referring to script kiddies, exploiters and URL sql injectors as hackers. Most of them can't even write a single line of html, let alone breach a server.
p/s server admins, you don't have to backup the entire site everyday, just backing up the mysql db is more then enough, and woudn't take up much space. You could even get a cron job to do the whole task for you at set intervals (5am usually works). Mysqldump usually does the trick. There are a couple of readily available php scripts as well. Try google :)