On the opposite side of the coin, the Archive may have more "historical" information about the Age itself, or details about the history/development of the KI that are outside of the scope of a walkthrough or guide, but visitors to the GoG website have no indication of where they might be able to find that information.
You're right, the DPWR covers the history aspects in greater detail, whereas the GoG takes a more "generalist" approach to its historical coverage.
What I'm proposing is a simple system of link-backs to various pages on our respective websites, so for example, DPWR's entry on Ahnonay would contain a link to the GoG walkthrough, and perhaps eventually a link to the GoC's map of the Age, should they release one. GoG's walkthrough and GoC's map page would both link back to DPWR's entry on Ahnonay in return (and perhaps even more ideally, link to each other as well), providing an interconnected resource of information that gives visitors and new players all of the information they need or want, without requiring them to stumble across all three websites on their own.
I do agree with you that there is a need to ensure that visitors aren't treated to a broken link when attempting to use one of these cross-links, and that is perhaps where most of the work will come in over the long run. However, I think good communication and cooperation will be able to head off many of these issues before they spring up.
Sounds good. But as you mentioned, communication is essential. To increase communication we would love to discuss specifics with you further on this thread at the GoG forum, where I'm sure you'll receive more input from our GMs than just me talking. I won't presume to speak for the guild; I'm sure each member can speak for themselves. I'll keep checking here frequently as usual.