Chessmaster is not available for Mac but there are plenty of alternatives that runs on macOS with similar functionality. The best Mac alternative is Scid vs. PC, which is both free and Open Source. If that doesn't suit you, our users have ranked more than 25 alternatives to Chessmaster and 13 are available for Mac so hopefully you can find a suitable replacement. Other interesting Mac alternatives to Chessmaster are XBoard (Free, Open Source), ChessX (Free, Open Source), DreamChess (Free, Open Source) and Shredder Chess (Paid).
Shane's Chess Information Database is a powerful Chess Toolkit, with which one can create huge chess databases, run engine analysis, or play casual games against the computer or online with the Free Internet Chess Server.
XBoard, also known as WinBoard on Microsoft operating systems, is a free graphical user interface client developed by Tim Mann that is compatible with various chess engines that support the Xboard Communication Protocol such as GNU Chess.
DreamChess is an open source chess game featuring "Dreamer", a moderately strong engine. Any XBoard-compatible chess engine (Crafty & GNU Chess) will work for varying degrees of difficulty. Includes 3D OpenGL graphics and various board sets.
Jin is an open source, cross platform, graphical client for chess servers, written in Java. Jin can run either as a standalone application (available at this website) or as an applet, directly from your browser (available at the chess server's website).