I’m certainly not in charge, but the situation isn’t complicated.There’s no Maxwell Plug-In which runs in V6 (Mac or Win) yet. All one can do is use the (fully featured) standalone option, Maxwell Studio – it imports 3dm files natively.
Those who have Rhino 5 on Windows may run Maxwell 4 (with the dedicated Rhino for Windows Plug-In) or the older Maxwell 3 (which used to ship with free Plug-Ins for a great variety of 3D-programs). Both Maxwell for Windows (V3+V4) Plug-Ins for Rhino 5 are powerful and feature complete.
Those who have Rhino 5 on Mac and Maxwell 4 may use the Rhino Plug-In for Mac. It is not feature complete though – it was a first effort to at all support the Mac crowd before a scheduled complete rewrite with a common codebase for Win and Mac.
I can’t say anything about the present state of development of Rhino 6 Plug-Ins. JD, the long time developer has left the company, his successor changed plans and got recently hired elsewhere. Now a third person seemingly has started working on the project. For more details better check the Maxwell forums.