Beamdog comes with it's own client, plus a steam key, so technically two copies.
Linux, MacOS and Windows are all supported (although only Windows has the Toolset supported, it can run reliably in Wine).
#NEVERWINTER NIGHTS ENHANCED EDITION LAGGING PATCH#
This is the most updated version content and patch wise, and only one for development. PC - Available from Beamdog, GoG and Steam.There are 6 official versions all containing the base Wailing Death campaign, Shadows over Undrentide and Hordes of the Underdark bundled together, some notes for each: