Of course there isn't a distinction between the two. When you fork a project (the XEmacs/GNUemacs kind of fork), you make a clone, and then make all the branding changes etc. There isn't any difference between the GitHub fork and a regular git-clone, other than the fork being made using the GitHub interface and is a first-class citizen of GitHub's interface. I would even go further and suggest Linus (or whomever came up with the term) decided to call the git-clone "clone" and not "fork" to avoid the connotation associated with project forking.
This was never a technical discussion to begin with, but one of accepted names.
Of course there isn't a distinction between the two. When you fork a project (the XEmacs/GNUemacs kind of fork), you make a clone, and then make all the branding changes etc. There isn't any difference between the GitHub fork and a regular git-clone, other than the fork being made using the GitHub interface and is a first-class citizen of GitHub's interface. I would even go further and suggest Linus (or whomever came up with the term) decided to call the git-clone "clone" and not "fork" to avoid the connotation associated with project forking.
This was never a technical discussion to begin with, but one of accepted names.