As you may have discerned from the IRS website; whether there are requirements for withholding and reporting will depend on the amount and type of income as well as the form of organization of the entity (or if it is an individual that is earning income) when a foreign person has income from United States sources.
More information is needed in order to give an answer that simply does not repeat all of the rules for all of the possible scenarios.
For example, if an individual earning wages from the foreign entity is simply making presentations without any deposits or money received there may not be any requirement for that foreign person in regard to income taxes. There may be visa or other considerations that are not tax related.
Perhaps if you can provide more information of the expected activity we can give some guidance (or at least references) for you to consider.