The MITRE Corporation (MITRE) grants you a non-exclusive, royalty-free license to use ATT&CK for research, development, and commercial purposes. MITRE does not claim ATT &CK enumerates all possibilities for the types of actions and behaviors documented as part of its adversary model and framework of techniques. Using the information contained within ATT&K to address or cover full categories of techniques will not guarantee full defensive coverage as there may be undisclosed techniques or variations on existing techniques not documented.”]
Source: https://collaborate.mitre.org/attackics/index.php/attackics:Terms_of_Use