The applications are designed to use multiple simultaneous inputs. However it depends on the method of using those multiple inputs. Applications used on a laptop or tablet can use a single input. However applications that use a large screen display or Huddlewall allow for many more inputs at the same time.
Large screen displays depend on the inputs being used and you should consult the manufacturer for exact input specifications.
The Huddlewall Interactive Wall solution can use 7 or more interactive pen inputs at one time.
Using the Paper application can be used to expand the number of inputs used with any of the systems you chose.