The Rich Application Client (RAC) is not the same as Active Workspace. Also, LDF is for "displaying" data from external systems (read only). I think you want TcIF (Teamcenter Integration Framework) for Polarion? See platform_extensibility_config.pdf.
I guess it depends on your use-case. LDF will show read-only data (one-way). If that's your goal instead of interacting with the Polarion data in Teamcenter then you're on the right track. My assumption is that you want a fuller integration where you can interact with it (two-way).