Indeed, it seems that there is no problem for controls developed on Silverlight or using HTML5 to be included in the Sandbox solutions for SharePoint Online. I will forward your suggestion to our Silverlight team so they consider adding our SharePoint Chart. As to the rest of the Web Parts we provided, I am afraid we will not be able to change them so they work for SharePoint Online. However we are eager to see how SharePoint 2012 goes and what we can do for you in this direction.
the Telerik team
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