As others have pointed, the team can take the domain from you at anytime. They might take it immediately, or wait for you to develop it.
What you can do, however, is contact the soccer team. Play it cool, and tell them you are a big fan, and you want to use the domain and develop it into a forum. Mention that you want to help the team, and you will be managing the forum by their rules. Make them assured that if something appears on the forum, and they don't want it there, they can call you anytime and have it taken down.
Tell them you will do all the work, and all you want from them is a written agreement from them to use the domain. If they decline, offer them a kind of partnership where you will split profits 50/50 with them while you pay for hosting and promotion. Only do that in case you think it will be profitable.
Just make sure they know you will play by their rules, and get a signed written agreement that they are OK with you, using the domain.
Good luck!