I have come in late to this debate so apologise if I am repeating any viewpoint that has been shared already.

There is a difference between K1 rules and K1 the brand. The brand is formatted in such a way that anybody wishing to advertise the fact that they are staging a K1 tournament or Grand Prix is asking for trouble and must surely be crossing the line.
Other infringements would be using only the limited weight divisions which would serve to mirror the K1 brand values.

However K1 rules are just another set of rules identified by the fact that they are fought in K1 tournaments. All that happenned here is that the wheel was re-invented.
In fact I would go so far as to say that it is just another version of modified Thai rules, modified a little more:)

If you take the weight divisions, round durations & format, this is not acceptable.

If you take the combat rules, add weight divisions, different round durations etc, all you have done is taken the rules, not the brand image.
K1 rules are quite a specific modification so I don't really know what else you can call them other than Kickboxing - which would promote confusion.

It is however true to say that there is "fashionable" leverage to be had out of the terminology. If you can measure that, then may be there is an arguement for infringement.

For me, it would be the simplist way to get the rules understanding across to the general public, as they are more familiar with the term K1 than perhaps International, oriental or modified rules as an explanation.

Is any of that right or wrong? I don't know. If K1 were to persue someone for using the rules, then may be they should be persued for modifying them in the first place.

If someone passes themself off as the K1 brand - thats a whole different story!