Will it keep existing deep links published in books and research papers from breaking? What prevents Google from setting the whole site into read-only mode as-is? Keep it working as it does now and disable changes.

Was that a rhetorical question--how could any third party possibly prevent deep links from breaking?

What is the criteria for "legitimate"? A project useful for me may not be "notable" enough for most to consider "legitimate".

Presumably, not abusing Google Code as a hosting site for pirated content.

Or for personal data. I've seen some people using Google Code as a pseudo-Dropbox. Clever, but ultimately not what the service was intended for.

Thanks for this, Chris.

Could you publish a list of projects w/descriptions? That would be great for others (gitlab?) who might want to host / cherry-pick / curate the collection a bit more than that.

I suggest letting developers to specify projects they find useful to be included in this cold storage.