There have been quite a few leaks over the past few days and it's no coincidence that this all occured after the platforms hit RTM. Joining the long list of RTM leaks is Visual Studio according to a post on Winunleaked.info. Additionally, the source states that no keys are needed for this build and it is reported to be untouched too (we cannot confirm this).
As with any leak, if you download it proceed at the risk of infecting your machine with malware as it is possible to bundle malicious software with these leaks.
The leaks are occurring because after a product hits RTM, many more individuals are able to get their hands on the platform. When a product is still being developed, those with access to the platform is highly restricted.
Over the next few days we expect the leaks to continue as more and more individuals get their hands on the final shipping code for several Microsoft products.