Just got it building with Mountain Lion, XCode 4.6.1. Here are the steps I had to take:
types.h:
1) Change:
typedef unsigned long ULONG; // Unsigned 4-byte int.
To:
#if defined (DSI_TYPES_MACINTOSH)
#include <MacTypes.h>
typedef UInt32 ULONG;
#else
typedef unsigned long ULONG; // Unsigned 4-byte int.
#endif
2) Search the project for:
IOCreatePlugInInterfaceForService
Directly above each call, there is a definition of score as "long score". Change long to SInt32 in each case.
3) Highlight the project file (ANT_Libraries, 5 Targets). Highlight the Project on the right side. In the "Build Settings" tab, change "Architectures" to "Standard (32/64 Bit Intel)." Change "Base SDK" to "Latest OS X (Mac OS 10.whatever)." Change "Compiler for C/C++/Objective C" to "Default Compiler."
4) In antfsmessage.h, comment out the error on line 23 and change each "0x__" on line 24 to "0x00" or your network key, whichever you've got.