Thank you for contacting us with this question.
I understand your concerns, but I want to assure you that there are no issues of legal matter regarding our themes. Microsoft is aware of the designs that we have. In some cases we are even following especially created by Microsoft UX Guidelines in order to comply with their own design - such an example is the recently introduced Visual Studio 2012 and the UX Guidelines that we followed for our Design-time Wizards, Toolbox and other parts of the suite in the context of the new Visual Studio: Telerik’s WinForms are now Visual Studio 2012 RTM Ready! Play with Metro Themes and Touch Gestures on Windows 8!
As to our themes, here is a blog post where we are announcing a new set of Office2010 themes: New Themes Coming to Telerik Windows Forms in Q1’11 and Why We Rebranded an Existing Theme.
I hope that this clarifies the situation. Do not hesitate to contact us if you have other questions.
the Telerik team