There are 2 classes of shares. Class A is common stock and can be sold at any time. The material sent by the Board is numerous and thick. I haven't gone through it all, so I don't know what the rules are for Class B shares. Members got half of their holdings in Class A and half in Class B.
Stock will be locked up for 6,12, and 18 months. 1/3 at a time will be unlocked. This is my understanding. Seat owners were given a chance to be selling shareholders in the IPO. I think a small amount will be sold this way. Most seatholders will wait. I hope this helps.