I tried to add one web parts which is available on your website.
1- PopularGroupRepository.cs is copied in Repositories folder
2- Mark-up and code files goes to MonoX/ModuleGallery/SocialNetworking
3- PopularGroupsList goes to App_Templates\CustomTheme\SocialNetworkingTemplates
It gives following Error.
Error 3 The name 'CacheRootKey' does not exist in the current context C:\Projects\TestProjects\NewProject\MonoX\ModuleGallery\SocialNetworking\PopularGroupsList.ascx.cs 134 76 Portal