Before asking the finder to start the application (if start=1 is specified), check that it isn't incidentally running already.
diff --git a/Mac/Lib/lib-toolbox/aetools.py b/Mac/Lib/lib-toolbox/aetools.py
index 42b6b76..1af761e 100644
--- a/Mac/Lib/lib-toolbox/aetools.py
+++ b/Mac/Lib/lib-toolbox/aetools.py
@@ -161,7 +161,10 @@
 		
 	def start(self):
 		"""Start the application, if it is not running yet"""
-		_launch(self.target_signature)
+		try:
+			self.send('ascr', 'noop')
+		except AE.Error:
+			_launch(self.target_signature)
 			
 	def newevent(self, code, subcode, parameters = {}, attributes = {}):
 		"""Create a complete structure for an apple event"""