I wonder if one could get some mileage out of making a distinction between natural persons (ie actual people) and other legal persons (eg corporations). Natural persons are the only people whose freedom we need to consider. Adding a clause to a free software license that required anyone who wasn't a natural person to follow the commons clause wouldn't impinge on the freedom of actual people. They would still be able to use the software in freedom even when working for a corporation(so no field of endeavor restriction). It is only the fake person that would be restricted. IANAL