As you know, you cannot install DPM 2007 on a Domain Controller. You will get the following error message when you try to install DPM 2007 on a DC:
But you can install DPM 2010 on a Domain Controller. Make sure to follow the Beta documentation to complete this installation. The direct and automatic installation from the CD will fail. So you need to perform a four step process (Create groups for SQL 2008 installation, Install SQL, Create Groups for DPM installation and install DPM) to complete the DPM 2010 installation on a Domain Controller.
Installing SQL or any applications on a Domain Controller is not recommended. But this option is useful when you are evaluating a product or doing a demo.