Can I buy the source codes, modify it and resell the helpdesk app to my clients?

You can modify the source codes, but NO you cannot resell or redistribute your derivative works in any way. If you want to install the tool at several client's of yours - you have to order a separate license for each.
Creation date: 12/12/2015 15:37 ()      Updated: 12/12/2015 15:37 ()
Jitbit Helpdesk ticketing system is our flagship product. Its a great helpdesk software app offered both as a hosted and "on-premise" versions.