In November 2016 there were changes made to release management licensing in Visual Studio Team Foundation Server and Team Services.

If you want to understand how concurrent pipelines are licensed (and indeed what they are!) then these are some good resources: a video – http://bit.ly/2j1rMKt, and blog entries for TFS – http://bit.ly/2iweV67 and TS – http://bit.ly/2j5CPGn.