Complex sentence: The computing department at the school uses mostly open source or free software including Linux but also has Windows XP and special, paid for applications in its DT department, and a Wiki is used for online communication of information between staff and pupils.
Split into simpler sentences: The computing department at the school uses mostly open source or free software including Linux but also has Windows XP and as well as specially paid for applications in its DT department. Also a Wiki is used for online communication of information between staff and pupils.