sitefinity (both community and standard) does indeed include full use of the telerik controls, provided of course you're using them within your sitefinity site.
however, i believe the demo you linked may be a bit outdated, as RadMenu.Net2 is the previous version of telerik controls. these have been replaced with the new Rad Web Controls in sitefinity version 3.5 (which I assume you're using?)
I think this link might be a better place to start: http://www.sitefinity.com/help/developer-manual/adding-modules-intra-bare-bones.html
as this tutorial looks like it uses the new telerik controls assembly that is included in the current version of sitefinity.
i hope this was helpful!