With all the talk of the way forward for the GTC I have put on my ‘lawyer’ hat and have a few suggestions. The point here is to maintain the original concept but avoid any complications for the organisers.
WARNING: Legal concepts follow, do not proceed if brain not in gear.

As the words ‘challenge’, ‘competition’, ‘association’ and ’team’ can be construed as an inducement to undertake an activity that may cause personal injury or financial loss, let’s drop these words.
Rename it the GPS Team Community, this removes any liability, indemnity or insurance issues.
So rather than thinking of it as a ‘challenge’ it is a place where groups of people socially connected can upload and compare the values read from their own GPS’s.
Rather than ‘Teams’ groups of individuals are know as ‘Families’, ‘Sets’, ‘Flocks’, ‘Herds’ or whatever term you want, just don’t call them ‘Teams’.
The webmaster/s are then co-ordinating a community not a competition, the sponsors are supporting the Australian GPS windsurfing community and the webmaster/s randomly award prizes.
Accomplishments are acknowledged by the awarding of trophies/medals to members and families in the community who values posted are worthy of recognition based on a method decided by the webmaster.
Members of the community may wish to contribute to the webmaster/s to help cover overheads and to acknowledge the contribution of the webmaster/s work in establishing and maintaining the community.
Publish the above as ‘Terms of use’ for the web site. Then no one has to sign any forms they just ‘By accessing this web site I acknowledge the Terms of use’
Sort of like MySpace for windsurfers with GPS’s