The kW Xport plug-in source is released under the MIT license. 
Basically, it means "feel free to use it; credit the source; don't sue me 
if something goes wrong."
Note that it requires a copy of the proprietary 3ds Max SDK installed to 
actually build. This would make the source incompatible with the GPL, so 
don't even ask about that. MIT is a better license anyway, IMO.

Feel free to contact me through my handle "hplus0603" at the site 
http://www.gamedev.net/