We have released a installer for Halo 2 base game, Project Cartographer and all required dependencies.
This download should be everything you need to install Halo 2 and play online. It installs the base game, launcher, Visual C++ 2005, .NET 4.5.2 and Directx 9. Installer source can be found here.
Its 3.2 gigabytes in size, it contains a fully updated base game with all the campaign maps.
Comment here or in the Discord help channel if there are any issues
Installer has been updated (1.2) with fixes and now includes some custom maps.