Unfortunately, for developers, the situation is reversed- it is free for us and other developers to make Kontakt-compatible instruments, but if we want to make a Kontakt Library compatible with Kontakt Player, there is a cost involved. For clarity, developers often call 'Kontakt' instead 'Full Kontakt'. 'Kontakt' costs $400, while Kontakt Player is free to download. Native instruments develops two different versions of Kontakt, one called simply 'Kontakt', and another called 'Kontakt Player'.