Because NASA is a federal entity, there are strict requirements for documenting non-mandated uses of NASA resources. Specifically, a formal agreement, known as a Space Act Agreement, (i.e.: MOU, MOA), shall be used whenever there is a commitment of NASA resources involving an entity other than NASA. The committed NASA resources may include time and effort of people and support services, use of facilities, use of equipment, and where appropriate, direct funding.
Which are you?