In visual studio, when you add a reference there is a flag in the properties called, \"Copy Local\". There is some confusion about what this actually does and when. It see
The Copy Local property determines whether a reference is copied to the local bin path. At run time, a reference must exist in either the Global Assembly Cache (GAC) or the output path of the project. If this property is set to true, the reference is copied to the output path of the project at run time.
So this property is actually not useful in your scenario.
I'm unable to suggest a better solution than adding the assembly to the GAC in each developer workstation: http://msdn.microsoft.com/en-us/library/yf1d93sz.aspx