Yes, a creative cloud subscription is required in order to be able to use Lightroom Mobile.
What Jim said.
"Lightroom mobile is included as part of the following Creative Cloud membership plans:
Creative Cloud Photography plan
Photoshop Photography Program
Creative Cloud complete plan
Creative Cloud Student and Teacher Edition
Creative Cloud for teams complete plan
If you have access to Lightroom 5 via your Creative Cloud membership, then you have access to Lightroom mobile.
Since Lightroom mobile is a service, it is available only via membership plans. Lightroom 5 perpetual license does not include access to Lightroom mobile."
Its too bad Adobe doesn't have a mobile app only plan, since I really don't need all the other stuff that comes along with the subscription to Creative Cloud.
Thanks for the info John.