Firstly, I would like to commend your efforts in taking over the running of the forums in the worst imaginable circumstances of "handover".
To be honest, I think that, as far as these forums are concerned, we need to acknowledge that the party's over. My seeming dismissiveness may be enabled by the fact that I've had to learn to "let go" of a number of things in my life over the past few years. In terms of member activity, the forums were already in decline while Seth was still with us, and I don't think his passing would've meaningfully exacerbated that trend.
Discussion boards typically depend on turnover of active members for their ongoing vitality. People join, eventually run out of things that they want to say, fade away, and are replaced by new, freshly-motivated members. I recall members here saying how they first heard about the Shangri-La diet from a programme segment on TV, or from a magazine article, or from Freakonomics. Then there were people like myself – in a country where the Shangri-La diet was not publicised, and where the book was not generally available – who heard about it by fluke in other circumstances.
The problem is that there is probably nothing fresh being broadcast / printed / blogged to attract the curious to the forums any more. People aren't hearing about the Shangri-La diet these days. There's a saying that "if you build it, they will come" – but they still need to hear about it first.
We reached "peak Shangri-La" some years ago, and I don't think that a return to those days could be realistically expected.
Morex makes a good point about "benefit to humanity", and I would commend his interest in personally preserving some of the content of the forums elsewhere for public accessibility. Given that I have above foreshadowed a probably poor return for effort in terms of likely new viewers, I would not expect it of anybody to undertake the Herculean task of migrating the forums to some other form of repository.
If I recall correctly, Seth had been working on a new edition of his book. Board members might take some consolation that the most recently available revision of the book – the one with the pale green cover that you can see on Amazon's website – took into account the experiences of the earlier "lab rats" here. Their legacy endures in the book.
Augustus, thank you for personally notifying above-newbie members of the likely fate of the forums. Ten weeks' notice of closure should be sufficient for members to archive from the forums what they would like to keep for themselves or re-publish.