The Free Software Foundation (FSF) defines four essential freedoms that software (and by extension, models or other works) must respect to be considered “free”:

1. Freedom 0: The freedom to run the program as you wish, for any purpose.
2. Freedom 1: The freedom to study how the program works, and change it so it does your computing as you wish.
3. Freedom 2: The freedom to redistribute copies so you can help others.
4. Freedom 3: The freedom to distribute copies of your modified versions to others.

Now, let’s analyze which ModelGo license options conflict with these freedoms:

1. BY (Attribution)

• Requires giving credit and retaining attribution.
• Conforms to FSF freedoms, as attribution alone does not restrict use, modification, or redistribution.

2. NC (Non-Commercial)

• Restricts use to non-commercial purposes only.
• Violates Freedom 0 (the freedom to use the software for any purpose, including commercial).
• FSF considers NC licenses non-free.

3. ND (No Derivatives)

• Prohibits distribution of modified works.
• Violates Freedom 1 (freedom to modify) and Freedom 3 (freedom to distribute modified versions).
• FSF considers ND licenses non-free.

4. RAI (Responsible AI)

• Imposes restrictions based on “responsible use.”
• Depending on the exact terms, this could limit freedoms (e.g., banning certain applications).
• If it restricts use cases (e.g., no military use, no surveillance), it violates Freedom 0.
• Likely non-free under FSF standards.

5. OS (Copyleft / Open Source)

• Requires derivatives to remain open under the same license.
• Conforms to FSF freedoms (this is how the GPL works).
• The FSF supports strong copyleft as long as it doesn’t restrict the four freedoms.

Conclusion:

The NC (Non-Commercial), ND (No Derivatives), and RAI (Responsible AI) options do not conform to the FSF’s four freedoms.

• NC restricts commercial use (violates Freedom 0).
  
• ND prohibits modifications (violates Freedoms 1 & 3).
  
• RAI may impose additional use restrictions (violates Freedom 0).

The BY and OS options are compatible with free software principles.