Per my previous blog post https://blogs.msdn.com/sandcastle/archive/2009/01/15/sandcastle-update.aspx, I have released the source code for the latest version of Sandcastle at https://sandcastle.codeplex.com/SourceControl/ListDownloadableCommits.aspx. This release was used to ship Visual Studio 2010 Beta 1 documentation (https://msdn.microsoft.com/en-us/library/dd831853(VS.100).aspx)
I am in the process of generating the msi and will be providing additional details on the release shortly. Please expect another blog with details by early next week. Cheers.