The creators of HitBall Virtual Dueling,
the sport described at www.hitball.org and duelist.biz, make it available to the public under the following terms and conditions:

You MAY:

...freely copy and distribute the rules and specifications of equipment from the above mentioned websites.

...make equipment for the game, brand it as you wish and profit from selling it.

You may NOT:

...patent, copyright or otherwise restrict free access to any intellectual property, production method, design improvement or variation developed for HitBall Virtual Dueling.
The conditions expressed here must be applied to any extension of the idea that you make.

The conditions expressed here apply to any device, scheme, concept, product or idea which derives from the sport, or from content of the websites, including, but not limited to:
materials and design of ball, line, elastic, harness, footwear, clothing, playing surface, electronic scoring systems, score display systems, performance enhancing substances, eyewear and protective devices.

The intention of this copyleft notice is to make HitBall Virtual Dueling available on the same (by analogy) terms as computer software released in terms of the gnu licence. Any doubt as to the intention of this notice should be interpreted in the light of the intentions expressed by the open source software movement.

These are described at: http://www.fsf.org/licenses/gpl.html http://www.gnu.org/copyleft/copyleft.html
and at: http://www.gnu.org/

Further information about copyleft: A New Scientist article, published under a copyleft.