For the officially released packages, the source code for Value Added Components is available in the package at the \Cpp-C\Eta\Impl folder (Reactor and RDM). You can download the ESDK packages from here.
Moreover, the source code is also available in GitHub.
Thanks. I'll mark it as accepted, although I haven't had a chance to verify. My understanding is that not all VA components might be open, but I'll need more time to check which are and which aren't. In the meanwhile we have been working without the binaries, and for our purposes that has been fine.
Thanks again for your prompt response.