I was playing another person on the Mac version of chess (version 2.4.1) and it appears that I have him checkmated (he is white, I am black). However, the game does not end. Is there a move white can make that we have overlooked?

That's checkmate. The knight can't be taken and the king can't escape.

A strange game. How did the King end up in f3 in the first place.
The free Macintosh chess game current version is 2.4.1 Copyright 2008. A GNU chess product.
Application Universal.
According to sources GNU Chess: Frequently Asked Questions
Apple's chess product has not been updated.
Normally even in the Monitor feature a Chess Software Program should indicate mate, or freeze if a move is attempted after mate.
Apple no longer included Chess in the latest Operating System.
The strongest Chess program for Macintosh available is Sigma/Hiarchs. Two versions.
One for the new Intel Macs. The other for all other Macs.
See: ATPM 7.02 - Review: Mac Chess Downloads
and
Sigma Chess - Macintosh Chess Software
SigmaChess does have a free version.
The full version for regular Macs is $15. Hiarchs additional cost.

My guess is that the king was on e2 and the rook put him in check, so he moved to f3 to attack the knight. It is a strange looking board.

The king was on e2 and moved away from the rook, but he did not move to f3 to attack the knight. The king moved to f3 to escape the rook. The knight moved from g4 to f2 to check the king. After that, we expected the game to end, but the game never said "checkmate". It is white's move now, but we cannot see a move for him to make.

If anyone has played human vs human in Mac OS X's chess, could you tell me whether or not your version of the game will declare checkmate if the game is over? Or will it say nothing?

Thanks for the replies.

The Apple product features:
Human vs. Computer (Computer has Black)
Human vs. Human
Computer vs. Human (Computer White)
Computer vs. Computer
Chess Variants:
Regular, Crazy Horse, Suicide, and Losers
Features:
The Apple Chess front end is a Cocoa application whose drawing code is based on the glChess OpenGL chess client. It communicates with the Sjeng chess engine which runs in a separate process. In OPENSTEP and Mac OS X up to version 10.2 (Jaguar), Apple Chess used bitmap graphics with a fixed, pseudo-3D, perspective, and used an early version of GNU Chess as the back end engine.
Chess can be also played using voice commands which uses Mac OS X's built-in speech recognition capabilities. Games can be logged using the log feature, which can include information such as names, dates, places, types of game and moves made.

In a test of Human vs. Human mode:
The Computer will not announce mate.
BUT, the Computer will not permit any moves to be made in a mate situation. I tested the product by deliberatly setting up a mate position.
The Vocal feature is indicated above. Note that the Vocal feature in Human vs Computer or Computer vs Human will announce moves.

Additional: Apple has a chess product for the Widget Application. Also
Reinfeld's 1000 mates is also available as a Widget.
Widgets available at Apple.com. All Widgets are free and work with OS X.

Mac OS X v10.5.6

Chess v.2.4.1:

GNU GENERAL PUBLIC LICENSE
Version 2, June 1991

Copyright (C) 1989, 1991 Free Software Foundation, Inc.
59 Temple Place, Suite 330, Boston, MA 02111-1307 USA


To do human vs human, go to "game", then select "new game" from the menu. You can then select from the following players and variants:

players:
-human vs human
-human vs computer (human = white)
-computer vs human (human = black)
-computer vs computer

variants:
-regular
-crazyhouse
-suicide
-losers

White had three other much safer squares to put his king. As you demonstrated, f3 was checkmate, as would have been f1. If your friend had chosen d1,d2 or d3 for his king, the game would have continued.

What appeared to be the more aggressive move actually 'forced' you to checkmate. The knight was attacked, it had to move. One of the squares would put the king into check! People love to put kings into check! What do you know, it wasn't just check it was checkmate!

At least that's how it would have been if I was black.

But you were up on material and most probably would have won even if your opponent has chosen a good square for his king.

From a search, GNU chess is no longer supported by Macintosh.
The latest version I have probably came with the Original version OS X.
Apple is indicating that there are several chess products for Widgets.
Sigma Chess with or without HIARCS is free. Limited to 1000 games per file.
Sigma has a feature which will indicate Mate.
Note there are several websites which contain Macintosh Chess. They are listed in the SigmaChess.com website.
In Chessforums.org, there is a Macintosh Listing of chess programs, and chess widgets. Search for Macintosh User Programs and Widgets, dated 7/2/08
GNU Chess:
GNU is an old product. Version 2 goes back to June 1991. Apple no longer supports the product. Version 2.4.1 according to the program last supported 2003, which is pre-OS 10.5.
For better Macintosh Chess -
Therefore recommended go to Sigma Chess - Macintosh Chess Software
Note: Jose Chess is also free. jose Home Page
CM 9000 for Macintosh is equivalent to CM 10 for Windows. CM9000 is the only Chess Master that will work with OS X.