From WxWiki

[edit] Carbon Code To Open URLs On WxMac

(Credits to Aj Lavin)

 #ifdef __WXMAC__                                                        
 #include <Carbon/Carbon.h>                                              
 #endif                                                                  
                                                                         
                                                                         
 bool openUrl( const wxString& url)                                      
 {                                                                       
 #if defined( __WXMAC__)                                                 
                                                                         
   ICInstance icInstance;                                                
                                                                         
   OSType psiSignature = '????';                                         
                                                                         
   OSStatus error = ICStart( & icInstance, psiSignature );               
   if ( error != noErr )                                                 
     {                                                                   
       return false;                                                     
     }                                                                   
                                                                         
   ConstStr255Param hint = 0;                                            
   long length = url.Length();                                           
   long start = 0;                                                       
   long end = length;                                                    
                                                                         
   ICLaunchURL( icInstance, hint, url.c_str(), length, & start, & end);  
                                                                         
   ICStop( icInstance );
 
   return true;                                                 
                                                                         
 #else                                                                   
                                                                         
   // *** Put your favorite wxMSW and wxGTK implementations here.        
                                                                         
 #error                                                                  
   return false; // Not implemented                                      
                                                                         
 #endif                                                                  
 }                                 

(Note thanks to Stefan Csomor)

and if you need it to work on non-carbon target, you may have to add

 #if !TARGET_CARBON                                                      
       err = ICFindConfigFile(icInstance, 0, nil);
 #endif                                                                  

in front of the ICLaunchUrl

(Documentation)

IC=Internet Control Panel.

See http://developer.apple.com/qa/nw/nw60.html and http://www.quinn.echidna.id.au/Quinn/Config/ for full documentation (under Programmer documents)