问题
Is mysql license needed for sites like facebook, twitter etc.. i dont know which category they fall into. thats why.
回答1:
No, they can use GPL which is freely available. They would need to make Software that links to MySQL like a library or is even based on MySQL GPL, too, but as far as I know, they are not doing any of that. Even if, the GPL would force them to pass on the source code to anyone to whom they give the binary. Since they are not giving away the binary to anyone, there would not be a problem either ;-).
来源：https://stackoverflow.com/questions/4895708/is-mysql-license-needed-for-sites-like-facebook-twitter