This is one of the only kitkat ROMS that still supports the atrix HD. I flashed the ROM through Philz recovery and it worked. I just wanted to share what I have learned to save people the frustration I went through. Please follow the steps below. I hope this helps.
This method is for the Motorola Atrix HD MB886 and is not garunteed to work on any other device.
Download the latest version of ASOB ROM for the Motorola Atrix HD MB886 from their downloads page. Be sure to save this to an external SD card so you don't lose it. You can do this by either changing the default download location in your browser or moving it to your SD a card with your favorite file manager.
Next make sure that you have an unlocked bootloader. I don't know for sure but It may not work if you don't. The easiest way to do this on the atrix HD is to install moto-pocalypes on your phone. This app will let you unlock your bootloader in one click. Unlocking your bootloader completely voids your warranty, but if you are rooted (which you should be) then your warranty should already be void. Make sure that you allow installation of unknown sources under security in your settings. Download and install the apk and open it up. Tap on unlock bootloader and wait. You should see your phone restart, if you see a warning saying bootloader unlocked when the phone powers on then your bootloader has been successfully unlocked.
When the phone finishes rebooting head over to the play store and install rashr flash tool. When it has finished installing open up the app. Tap the recovery button and you should see a list of custom recoveries to download and install. Choose Philz custom recovery and click on the lastest version.
Warning: flashing custom roms can wipe your device or worse. Be sure to back up your system and go forward at your own risk.
When philz recovery has fishished flashing power off your device. You will now need to boot into recovery mode. To enter recovery mode hold down the volume up and power button at the exact same time and hold them down until your phone powers back on. If it does work the first time try again it may take some getting used to. Once you are in recovery the first thing you want to do is backup your system. Even if you have made a previous backup it is safe to make another one here so you don't run into an issues with compatibility.
Tap on the backup and restore option then tap on back up to external SD. Again be sure that you back it up to an external SD so that it wont be lost. When you back up is complete go back to the home screen by pressing the back button or the home button located in the bottom of the screen.
Next tap wipe/ format system. Tap yes I will install a new ROM and wait for the wipe to complete. Once you have wiped your system go back to the home screen and tap install .zip from SD card. Then tap on install zip from external SD card. Locate the .zip file from the ASOB website you download to your external SD card card earlier. Tap yes to confirm your installation.
When the flash is complete you will see a message saying install complete. Now reboot your phone. Give it a second. You should see your new kitkat ROM booting.
I hope that this tutorial helps. I have attached both needed apk files with this post. The ROM is to big to attach to the post and I cant post links yet. Just do a quick Google search for ASOB ROM and go to the developers website. Then head over to downloads and search for Atrix HD you should see a list of releases for the MB886.