bongblaze

With all the addons that come with XenForo and the general easy to create addons you could very quickly turn it into a private tracker even if you just index torrents. There's UNIT3D too, which is an entirely different script if you really just want a tracker. It's free and with some tinkering isn't too hard to install. But customization for such a thing would require more resources as its not readily available like Xenforo addons or ipb. One thing to keep in mind though is you need a website that offers root access to your server if you wish to run your own tracker.

I came across a website the other day that is rewriting XenTT for Xenforo 2.x, not sure how long it'll take though. If you just want to index torrents, not actually have your own "tracker" you can just hire a developer to build a page like that so it can easily list torrent peers. Should be a cheaper option than to build a tracker.