Flare is a gametype editor meant for server owners who hate using Halo's gametype editor to edit every single gametype. Halo's gametype editor is adequate for most purposes, but navigating through it is slow, and being only able to edit gametypes in the savegames folder makes it a bigger pain to transfer gametypes to a server. This program does not require gametypes to be in a savegames folder, it is organized with efficiency in mind, it is more expansive than Halo PC's gametype editor, and can make gametypes that are simultaneously compatible with Halo PC (including Halo PC for the Mac and HaloMD) and Halo CE.
It supports only Windows 7, Windows 8, and OS X 10.7 or higher. I can't guarantee it'll work on Windows XP because Microsoft considered it dead on April 8, 2014.
To point out the main features that this gametype editor has over Halo's built-in gametype editor:
More customizable game variants; much more freedom over your gametype than the stock gametype editor
Support for up to 7 vehicles for one type of vehicle on one side of the map rather than 4, if the map supports it
Game variants will work on both versions of Halo rather than the version that it was created in
If you're using Windows and -path is not set in the Halo executable's arguments, your gametypes are stored in a default path relative to your documents folder. In OS X, it's always going to be relative to your documents folder.
On Windows, it's at: Home Folder > Documents > My Games > Halo (or Halo Custom Edition) > savegames
On OS X, it's at: Home Folder > Documents > Halo (or HLMD for HaloMD) > savegames
Remember that the file name of all gametypes is blam.lst, and they must be placed in a folder inside the savegames folder. The folder can be any name, but you'll want to have it be the same name as your gametype to avoid confusion.
You are allowed to mirror these files, but you must know that it can update any time.
Let me know if there are any issues or bugs. Remember that Halo cannot show you nonstandard settings in its gametype editor, and Halo CE will be unable to show nonstandard settings in F2. By nonstandard, I mean like having 120% health or 25 point Juggernaut or even 100 kill Team Slayer.