You may or may not have been compromised if you had used it before, which a lot of people have since it's a popular source of free Steam keys.
The data stolen from the forum includes full names, usernames, scrambled passwords, email addresses, dates of birth, join dates, avatars, Steam usernames, and user activity data. Facebook access tokens were stolen for those who signed in with their social account. If you were you'd be listed on https://www.leakedsource.com/
They deny a hack but it's been confirmed by a user that his info is on there and that it was from dlh. So their denial is refuted. Just letting you know so you can do any damage control if you were compromised. Sites aren't 100% secure and eventually get compromised (it has happened with Steam). Damage control is just a part of signing up for anything.