Why Microsoft released the same dll/namespace name i.e. Microsoft.ServiceBus.DLL for Windows Service Bus and Azure Service Bus?

• Microsoft.ServiceBus.dll -- Vesion 1.0 -- for Windows/Enterprize Service Bus

• Microsoft.ServiceBus.dll -- Vesion 3.0 -- for Azure Service Bus

Why Microsoft released with the same name DLL/NameSpace name for two different things?

Due to this in my webapplicaiton I can't able to make a switch at runtime for windows/azure service bus decision.