It would be better to contact the published of the code though its blog and ask him for the changes you want to make, since this is a particular custom implementation. Thus, you will receive an answer directly from the person that crated form builder.
All the best,
the Telerik team
Do you want to have your say when we set our development plans?
Do you want to know when a feature you care about is added or when a bug fixed?
Telerik Public Issue Tracking
system and vote to affect the priority of the items