You and others may be interested to know that the way you have described these, they are not "legit" keys. This may be an unintentional misrepresentation. A better term might be "working" keys.
MSDN subscriptions provide working keys to developers for development purposes. They don't use technical enforcement to prevent you from giving the keys away, they use the honor system. They are legit only when used by the developer they are licensed to, and even then, the usage is restricted.
Someone who wants a key that "works" will probably be satisfied by these keys (perhaps more than satisfied, most MSDN keys will work for 5-10 activations). Someone who wants their software to be properly licensed for whatever reason won't be getting what they probably think they were promised, as legally, their software is equivalent to being pirated.
True enough, my wording could be determined 'misrepresented'. Though, by legit, I mean the keys I supply will not turn out as "in-use" or false. I mean, of course I know it is 'pirating'. But, I have had a MSDN since 2004, at $1k annualy.. I think I own quite a bit of copies of Microsoft products. But, thank you for your head's up.