What does the ruling of "no sin" apply to?

Imām Ibn al-Jawzī (d. 597/1201) summarized the scholars' opinions in his book "Zād al-Masīr" as follows:

1. It refers to ceasing to provide maintenance if they leave before the end of the year.
2. It refers to not preventing them from leaving, because staying for the year was not obligatory upon them.