can any one clarify if the product "D0GNQLL" 'IBM Rational Team Concert Developer Floating User License + SW Subscription & Support 12 Months' provides support for IBM System z, IBM iSeries on IBM Power and IBMz/OS on System z

The license you mention supports basic development on System z and IBM i - it includes a green screen 3270 client for z/OS developmentr and  has simple build capabilities client BUT to get the full feature set most z and i development teams  require (dependency build, promotion, deployment etc..) you need Rational Team Concert Developer for IBM Enterprise Platforms which includes all the capabilites of the developer licences plus extensions specifcally designed to facilitate z and i development . The equivalent floating user license key is D0GLSLL

The additonal features are described here

https://jazz.net/products/rational-team-concert/features/enterprise