14 DAY TRIAL // Even though Microsoft initially planned to launch Windows 8.1 for everyone in October, the company had a change of heart a few hours ago and published the RTM version on MSDN and TechNet, in order to give more time to devs to prepare their apps for the launch.
And still, many of them are already running Windows 8.1 RTM, as the OS update got leaked in late August for both 32- and 64-bit configurations.
Now it appears that the leaked builds are basically identical to the ones published on MSDN and TechNet and hash checks indicate that all versions that reached in the web in the last few weeks come from Microsoft.
This could also be the reason why activation is possible with a legitimate Windows 8 key, so running a leaked build might after all be as safe as it could be.