I didn’t even mean to find this out and, after purchasing 5 different copies, I mistakenly used the same serial on 3 different computers and have not received any errors when working in the program simultaneously. This is probably because they also did not put any mechanism in place to stop you from installing your version of Microsoft Office 2011 for Mac on as many computers as you want.
Microsoft did not make it very easy to deactivate a product key for Microsoft Office 2011 for Mac.
