As has already anwsered the files could be found on GitHub, since feather, feather widgets and packages are open source. You should check the file for the according version, as well, or decompile the used assemblies.
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 Sitefinity CMS Ideas&Feedback Portal
and vote to affect the priority of the items