I'm having the exact same issues. I downloaded the firmware and mono but when I try to execute the apex flash utility through the Mac Terminal I see an icon pop up in my dock and then quickly disappear and I'm left with the following message:
Last login: Thu Mar 12 09:04:09 on console
nicholas-grants-macbook:~ Nick$ mono "apex flash utility.exe"
Unhandled Exception: System.NullReferenceException: Object reference not set to an instance of an object
at System.Drawing.Graphics.Dispose () [0x00000] in <filename unknown>:0
at (wrapper remoting-invoke-with-check) System.Drawing.Graphics

ispose ()
at System.Drawing.Bitmap..ctor (System.Drawing.Image original, Int32 width, Int32 height) [0x00000] in <filename unknown>:0
at System.Drawing.Bitmap..ctor (System.Drawing.Image original) [0x00000] in <filename unknown>:0
at (wrapper remoting-invoke-with-check) System.Drawing.Bitmap:.ctor (System.Drawing.Image)
at System.Windows.Forms.Cursor.ToBitmap (Boolean xor, Boolean transparent) [0x00000] in <filename unknown>:0
at System.Windows.Forms.Cursor.CreateCursor (System.IO.Stream stream) [0x00000] in <filename unknown>:0
at System.Windows.Forms.Cursor..ctor (System.Type type, System.String resource) [0x00000] in <filename unknown>:0
at System.Windows.Forms.Cursors.get_SizeNWSE () [0x00000] in <filename unknown>:0
at System.Windows.Forms.SizeGrip..ctor (System.Windows.Forms.Control CapturedControl) [0x00000] in <filename unknown>:0
at (wrapper remoting-invoke-with-check) System.Windows.Forms.SizeGrip:.ctor (System.Windows.Forms.Control)
at System.Windows.Forms.ScrollableControl.CreateScrollbars () [0x00000] in <filename unknown>:0
at System.Windows.Forms.ScrollableControl..ctor () [0x00000] in <filename unknown>:0
at System.Windows.Forms.ContainerControl..ctor () [0x00000] in <filename unknown>:0
at System.Windows.Forms.Form..ctor () [0x00000] in <filename unknown>:0
at ApexFlashUtility.StandardWindow..ctor (ApexFlashUtility.ApexController controller) [0x00000] in <filename unknown>:0
at (wrapper remoting-invoke-with-check) ApexFlashUtility.StandardWindow:.ctor (ApexFlashUtility.ApexController)
at ApexFlashUtility.Program.Main () [0x00000] in <filename unknown>:0
nicholas-grants-macbook:~ Nick$
So has anyone figured this out?