SCO tried but everything had been permissively licensed or had not been properly treated when you still needed to apply copyright notices everywhere for copyrig

SCO tried but everything had been permissively licensed or had not been properly treated when you still needed to apply copyright notices everywhere for copyright to apply. There is also the counteracting market force that single source illiberally licensed API's are unappealing to users so in many cases granting rights to other implementations can be commercially desirable for the creator of the API. Mono's existance encourages .Net and C# adoption. Also there is the distinction between copying an API to duplicate it and USING the API to develop a program against (this would the speaking a language aspect). I would argue that using the API would never be infringement but would in all circumstances I could imagine would be fair use.