First: Path problems: it does not start. If you fix path... 
Launch an exception:
[Info  16:19:10.923] Running Banshee 2.6.1: [git-checkout (darwin11.4.0, x86_64) @ 2013-04-19 10:31:24 CEST]
Exception has been thrown by the target of an invocation.
System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.DllNotFoundException: glibsharpglue-2
  at (wrapper managed-to-native) GLib.Thread:glibsharp_g_thread_supported ()
  at GLib.Thread.get_Supported () [0x00000] in <filename unknown>:0 
  at Banshee.Gui.GtkBaseClient.InitializeGtk () [0x00000] in <filename unknown>:0 
  at Banshee.Gui.GtkBaseClient.Initialize (Boolean registerCommonServices) [0x00000] in <filename unknown>:0 
  at Banshee.Gui.GtkBaseClient..ctor (Boolean initializeDefault, System.String defaultIconName) [0x00000] in <filename unknown>:0 
  at Banshee.Gui.GtkBaseClient..ctor () [0x00000] in <filename unknown>:0 
  at Nereid.Client..ctor () [0x00000] in <filename unknown>:0 
  at (wrapper managed-to-native) System.Reflection.MonoCMethod:InternalInvoke (System.Reflection.MonoCMethod,object,object[],System.Exception&)
  at System.Reflection.MonoCMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) [0x00000] in <filename unknown>:0 
  --- End of inner exception stack trace ---
  at System.Reflection.MonoCMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) [0x00000] in <filename unknown>:0 
  at System.Reflection.MonoCMethod.Invoke (BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) [0x00000] in <filename unknown>:0 
  at System.Reflection.ConstructorInfo.Invoke (System.Object[] parameters) [0x00000] in <filename unknown>:0 
  at System.Activator.CreateInstance (System.Type type, Boolean nonPublic) [0x00000] in <filename unknown>:0 
  at System.Activator.CreateInstance (System.Type type) [0x00000] in <filename unknown>:0 
  at Banshee.Gui.GtkBaseClient.Startup () [0x00000] in <filename unknown>:0 
  at Hyena.Gui.CleanRoomStartup.Startup (Hyena.Gui.StartupInvocationHandler startup) [0x00000] in <filename unknown>:0 

Unhandled Exception: System.TypeInitializationException: An exception was thrown by the type initializer for Gtk.Application ---> System.DllNotFoundException: glibsharpglue-2
  at (wrapper managed-to-native) GLib.Thread:glibsharp_g_thread_supported ()
  at GLib.Thread.get_Supported () [0x00000] in <filename unknown>:0 
  at Gtk.Application..cctor () [0x00000] in <filename unknown>:0 
  --- End of inner exception stack trace ---
  at Hyena.Gui.CleanRoomStartup.Startup (Hyena.Gui.StartupInvocationHandler startup) [0x00000] in <filename unknown>:0 
  at Banshee.Gui.GtkBaseClient.Startup[Client] () [0x00000] in <filename unknown>:0 
  at Banshee.Gui.GtkBaseClient.Startup[Client] (System.String[] args) [0x00000] in <filename unknown>:0 
  at Nereid.Client.Main (System.String[] args) [0x00000] in <filename unknown>:0 
[ERROR] FATAL UNHANDLED EXCEPTION: System.TypeInitializationException: An exception was thrown by the type initializer for Gtk.Application ---> System.DllNotFoundException: glibsharpglue-2
  at (wrapper managed-to-native) GLib.Thread:glibsharp_g_thread_supported ()
  at GLib.Thread.get_Supported () [0x00000] in <filename unknown>:0 
  at Gtk.Application..cctor () [0x00000] in <filename unknown>:0 
  --- End of inner exception stack trace ---
  at Hyena.Gui.CleanRoomStartup.Startup (Hyena.Gui.StartupInvocationHandler startup) [0x00000] in <filename unknown>:0 
  at Banshee.Gui.GtkBaseClient.Startup[Client] () [0x00000] in <filename unknown>:0 
  at Banshee.Gui.GtkBaseClient.Startup[Client] (System.String[] args) [0x00000] in <filename unknown>:0 
  at Nereid.Client.Main (System.String[] args) [0x00000] in <filename unknown>:0 

It is not a missed library, because LIBRARY glibsharpglue-2 exists: Applications/Banshee.app/Contents/Resources/lib/libglibsharpglue-2.so