If you have bought license for UFT , it covers all addins.
UFT 11.5 needs "Unfified functional Testing" license type to utilize all its new features like API testing and Flex add-in.
if you have old license type "FT-Unified" and "FTAddins" ( which is for QTP 10 and QTP 11 ) , you will be able to use UFT with major add-ins like Java , .Net , orcale , SAP and so on.
But new add-ins like Flex , and new functionality of API testing will not be available.
Regards,