Since you got both from the App store they are linked to your AppleID. To comply with the license, technically you should roll back to whatever OS came with the system.
Thanks for this. I assumed it would be this situation, however when you install ML it updates the recovery drive. Doesn't that make it machine specific?
No. You can boot from an external drive or USB key and format the entire drive including the Recovery HD area and install any compatible OS X version back to the system.
The key is when you are in Disk Utility to click on the drive name (like Samsung 128GB blah blah) and not Macintosh HD when you reformat.
Once you install the OS anew from a USB drive you will have the possibility to erase the hard drive and your ID will no longer be tied to the computer since you delete all of the files.