Tournament Licenses

http://support.steampowered.com/cgi-bin/steampowered.cfg/php/enduser/std_adp.php?p_faqid=172

All tournaments involving Valve products require a "Tournament License". The Tournament License itself is free and gives you the authority to run a tournament.

Most tournaments that are held around the world require the participants to bring their own software licenses and/or PCs. However, if you do need additional licenses for your event, you can purchase temporary tournament subscriptions for a small administration fee. For a successful launch of your tournament, we require at least 5 business day prior to the start of your tournament to allow enough time for set up and your testing the accounts.

Please see the Tournament Licensing page for more information or to sign up: http://www.steampowered.com/?area=tourney_limited