Please take a look at this forum thread
You can use a decompile tool to see the code from the assemblies. The source code is distributed as an option for Enterprise edition, but you cannot use it to compile dlls and use them, since we don't give the key signer.
the Telerik team
Do you want to have your say in the Sitefinity development roadmap? Do you want to know when a feature you requested is added or when a bug fixed? Explore the Telerik Public Issue Tracking
system and vote to affect the priority of the items