But it's not just about the source... it's about the community, the support from the original authors, the available knowledge and comprehension that transcends wiki docs, as well as having a team large enough to be able to realistically continue its development in the foreseeable future. To lose these things abruptly doesn't mean that all the source code was deleted but rather that the virtual ecosystem was.
Feh. Those things you mention (the original authors, the development team, the community, website and other resources) aren't guaranteed regardless of how badly one would like them to persist. The source and the freedom to do something with it are what the licence grants. Everything else is gravy. Without the source the virtual ecosystem is useless; with the source one person can continue the project, even if only for personal use. The virtual ecosystem can be recreated by anyone who wants badly enough to continue developing the software, just like it was the first time. So it is really just about the source.