Over on the Magic Lantern forum a user was trying to install the latest version of the third party software, but was unable to. Their camera has firmware 1.3.3, while Canon has only made version 1.2.3 available on their site. There is no word on what features or fixes have been made available in Canon's official firmware version 1.3.3.
“Few weeks ago I bought a 5D M III. Today I tried to install Magic Latern, but I failed. The firmware version of my camera is 1.3.3, and there was no ML installation file for this version. Then I visited Cannon's website to download firmware 1.2.3. I tried to install 1.2.3, but my camera said ‘Firmware older than Ver. 1.3.0 is on memory card. Delete old file and update using later version.'. One thing I was surprised about is that there is no firmware 1.3.3 on Cannon's webpage. It is very strange that my camera is running 1.3.3 firmware.”
Source: [Magic Lantern]
Image Credit // Xitek Forum