Patched OSInstall.mpkg and OSInstall framework to allow installation on MBR partition.
To use these patched files you must create an installer using this method (Pandora's Box should also work). You can't just run the app downloaded from Mac App Store.
After creating the installer, run this command in terminal replacing "installer volume name" by the name of your installer drive. If it contains spaces, surround the name by " or precede each space with \ (you can just drag and drop the drive to terminal when typing the command)
sudo tar zxvf ~/Downloads/Mavericks_10.9.5_MBR_Patch.tar.gz -C /Volumes/"installer volume name"
If you download with Safari, it will automatically expand the gz, so the command should be
sudo tar xvf ~/Downloads/Mavericks_10.9.5_MBR_Patch.tar -C /Volumes/"installer volume name"