Plug-ins are generally considered a derived work, if directly written to use a specific API. You would need to build a module that works for many different systems and only uses the Plane APIs as a shim.
Even then, the shim might be argued to be infected, and thus the rest of the module too. In that case, you still could be facing an expensive and risky lawsuit, because I don’t think there are any precedents to predict how those winds will blow.
