"What part of Dreamweaver CC 2015 works when you don't have a CC paid subscription."
None of it.
Dreamweaver CC won't open unless you have a paid subscription or a 7 day free trial membership to Creative Cloud. Unless you cancel it beforehand, the 7 day trial automatically converts to a paid plan on the 8th day of service. Thereafter, Creative Cloud renews automatically each year until you cancel.
How to Cancel my Subscription?
The Subscription & Cancellation TERMS:
Nancy O'Shea, Product User & Community Expert
Alt-Web Design & Publishing ~ Web : Print : Graphics : Media