We'll own it

From Well Designed Urls WiKi

The problem with modifying the Source Code for (Open-source) apps is that after you've modified it you've Forked the Code and now you "own" maintenace of that forked version for as long as you plan to use it.

A far, far, far better solution is to use applications with a "Plug-in" Architecture so that you can write modifications without having to modify the core source code of the application.