Yes, I know that the quote you have typed above is an infamous Rousseau quote but it has been promulgated that Rousseau concludes Man if forced to be free!! I think what it means is if one man does not participate on the General WIll then Rousseau says such a man should be forced to, thus he is forced to be free!!!
I think thats what it means, the Link you posted is also invalid so i you could find another way to post it it weould be much appreciated!
It is only possible to be free if we understand reality. If we do not understand reality we are not in a position to make a free judgement, we struggle in vain against that which we do not understand. If an individual does not want to obey the general will then he must be "forced to be free". Imagine a group of people attempting to cross a bridge that is, unknown to them, weak and dangerous. The gatekeeper refuses to let the group pass and they feel that their freedom is being curtailed as they do not have a full understanding of the situation. The gatekeeper is forcing them to be free; if they were not stopped then they may have perished on the weak bridge. Rousseau likens this situation to the person who does not understand why they should obey the general will. To obey what is best for all is to maximise the freedom for each.