Glest seems to use the
Abstract Design Pattern which provides a way to encapsulate a group of individual factories that have a common theme, such as using different sound libraries for different OS types. (In the shared_lib/sound folder there is a folder for direct sound 8 and openAL. On a Linux system the direct sound files are ignored and the openAL files are used.)
If the compiler complains about not finding the DirectX libs remove the encapsulated dx files from the project include files.
Mac uses OpenGL for graphics and can use
http://www.un4seen.com/ (is free for non-commercial use) for sound. I think
xerces can be compiled under Mac.