Can't get FlagRSP to work

So, I've been a huge RPer for a long time on retail, since end of TBC certainly, and I was really looking forward to the idea of RPing on this private server as well. When I saw this forum post, I decided to give it a shot and downloaded the top .zip file of the page (the one with the most downloads) and extracted it to my addons folder. However, unlike every other addon I've chucked on, FlagRSP just refuses to work, and i'm not sure why.
Anyone with a bit more technical aptitude able to give me a hand? I'd be very grateful.
Anyone with a bit more technical aptitude able to give me a hand? I'd be very grateful.