I apologize, I misled you.
Although, you can create a new silverlight project (without using the telerik templates) and manually add telerik controls to the xaml, the controls could appear without errors, but most of the functionality will not work.
For example, I have created a new SL 3 project, added references to the SL4 Telerik assemblies and bound a gridview. The page shows fine, the gridview is rendered fine, but its main functionality like Filtering, grouping, sorting do not work.
So, the bottom line is that you do need VS 2010 (even the free Express edition) and Silverilght 4 to run the RadControls for Silverlight 4.
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