It seems like the author of this great mod is not supporting it anymore.

http://wow.curse.com/downloads/details/9924/

smariot said
Jan. 30, 2008, 11:32AM (2 days, 5 hours ago)

It wasn't a mistake, I don't want to be bothered with maintaining this project. I learned Lua and played around with an interesting software problem, and now I'm done and want to learn about something else now.

Absolutely all the software I had access to to create this can downloaded for free. Linux, Wine, SciTE, and even Warcraft itself can be downloaded for free, although you'll of course need to pay for your account.

The extra bits and pieces of QuestHelper that aren't included in the downloads here are in the Git repository. I know it's a bit hackish in places and the code isn't well commented so it's a bit of a mystery what the hell I was thinking when I wrote it, but anyone that can manage to understand it well enough that they can make changes to it is welcome to do so.

And just as a warning, I expect the release of the next expansion pack to break QuestHelper.