Hello everyone. I have been working on and off with Zaid to create a new Halo modding application. We "resurrected" Abide and changed a lot of the core code. It supports AddOns with the addition of the Abide AddOn API. Its hosted on CodePlex so you can download the source code and do whatever you want with it. If you want to download it (or the AddOn templates) you can visit the CodePlex page:
https://abide.codeplex.com/
Latest Release is Abide Halo Map Editor RC 1.4.0.11
I am aware that Halo 2 modding is quite dead. I made this because it was fun to program. If it never gets used, that's OK but if you are interested, please download and give it a try.
It supports Halo 2 and Halo 2 Beta maps. I intend to add support for more such as Halo CE, Halo 3, and Halo: Reach.
Abide AddOns Thread:
viewtopic.php?f=10&t=2284
Images:
Thanks.