Hi hmosiejones,
Each user who uses Office Professional Plus needs a license. Each license you can install on at most 5 computers.
For detailed information:
http://technet.microsoft.com/en-us/library/gg982959
http://office.microsoft.com/en-us/access-help/reactivate-subscription-license-by-using-osaui-exe-HA102053194.aspx?CTT=1
Thanks,
Bourne Zhang