cmalakar is right - you have missing libraries
You do not need to install anything - all you need is the jar file in the external folder of the ant... And as far as I remember you also need oro. You do not need to build it (this is where you need maven I believe), simply download the jar
You might also read through
http://www.opensubscriber.com/message/user@ant.apache.org/2866650.html (go up and down the thread for all ideas and proposals) -- your ant just need to be configured to use the proper libraries (and you need to have them)