I made a note on the page a while ago and was hoping I could get more information. Can you look at comment 2 http://senseis.xmp.net/?Ko#2 and tell me what you think? -Sam
How about: you may not immediately capture the stone that your opponent played to capture one (and only one) of your stones.
The suggestion at ko#2 is very concise, but I personally find it somewhat difficult to parse.
The article attempts to explain the ko situation without the ko rule, and hence motivates the necessity of the ko rule. Once you know what is a ko, then you can simply reference it by saying things like "taking the ko", "recapturing the ko", etc.
Personally I like this approach, and have attempted to clean up the circular references. If need be, a further improvement would be to stress the infinite repetition aspect.