Both WorkGroup and Floating License Server are server-based applications but they work in different ways.
WorkGroup is used to keep all your data secure and can be shared among authorized WorkGroup users only.
The Floating License Server is used to share licenses for the GeneSpring client. The analysis done by multiple users cannot be shared, though it allows multiple users to share a single license with many concurrent keys at any given time. The Floating License Server can be used in conjunction with GeneSpring WorkGroup or GeneSpring Desktop versions, but WorkGroup is also a standalone application.