Currently, if a page's font size is just a little bit larger (for example 14px), some widgets do not display correctly. Sometimes the images alignment is wrong, sometimes borders do not fit. As an example, look at...

http://www.kendoui.com/forums/ui/general-discussions/widget-display-with-changed-font-size.aspx

With frameworks like Bootstrap it is quite common that the font size is not too small. So currently it means work to use Kendo and Bootstrap together,

I suggest you either improve the widgets' rendering so they do not rely on a certain font size. Or another solution would be if each customer could create a specific CSS from the LESS by setting some variables.