[baldajan]

It's not copyright, but trademark (it's a subtle, but important distinction). And for trademarks, the short answer is it depends. Some trademarks have no protection (generics or ones that become generic) and others have infinite protection (famous marks, like Apple and Disney). While most have protection in their field (think the word Mac, it's a computer, a burger and a cusmotic brand).

Field however is hard to define, for example Trademark offices have categories and theoretically, you cannot have 2 trademarks owned by 2 different entities. That said, it does happen, because the "fields" are actually defined by likelihood of confusion, which is shown in court. If this is all confusing, it is.

But long story short, if your mark is famous (and kik's would be considered famous), you're the only one allowed to use it, and you HAVE TO in force it, otherwise, you lose it.