The Trac application does not use Apache to serve the web site. You do not need to install Apache on the server for the Trac application, however, most Macintosh installations will have Apache already installed and some server ports are reserved for the Apache web server application. By default, all web server applications serve on port 80, so Apache and your Trac application will have a conflict and your Trac application will not be able to serve its web pages. The Trac application may be modified to serve on a different port in order to allow both applications to serve web pages.
To change the server port, open the file Prefs.INI that is located in the Trac application folder. You can use TextEdit to edit the Prefs.INI file. Locate ServerPort=80. Change 80 to 20000 to serve the Trac application on port 20000. Restart the Trac application and it will now be serving its web pages on port 20000 (or another specified port).