The possible GPL violating Microsoft tool WUDT was first called into question by withinwindows.com. According to this site, Windows 7 USB/DVD tool from the ESD version of Windows 7 which can be used to create a bootable USB medium or a DVD contains code which does not originate from Microsoft and therefore is covered by the GPL.

After this information began to circulate, Microsoft removed the freely available software from the website and announced they would look into the matter. The community manager Peter Galli of the Microsoft facilitated Open Source site port25 confirmed that an infringement of the GPL was indeed the matter at hand:

"After looking at the code in question, we are now able to confirm this was indeed the case, although it was not intentional on our part. While we had contracted with a third party to create the tool, we share responsibility as we did not catch it as part of our code review process. We have furthermore conducted a review of other code provided through the Microsoft Store and this was the only incident of this sort we could find."

Allegedly, the software did not come from Microsoft and Microsoft did not pay close enough attention while reviewing the code. This slip provided the motivation for the company to examine further software for possible GPL infringement and upon doing so established that no other software was the cause of such a breach.
In order to comply with the terms of the GPL, Microsoft now needs to license the tool under the GPL. The source code of the tool is to be released next week.