>Sure will make for an interesting addendum to some famous persons biography.
The copyright status of forum posts probably means that they'll never be included in any book or work written this century except in the very limited form allowed by their authors. (Assuming that the current copyright ridiculousness is not quelled.) Which is too bad, as they're pretty interesting and I doubt their authors care so much unless you got rich off them.
Summarising and paraphrasing what someone else wrote publicly is totally ok and legal. Biographers can at the very least use all the available material for their writing. Even quoting non-substantial parts of someone else’s writing – something that could be copyright infringement – is pretty uncontroversial and legal. It falls under fair use. And not the wobbly part of fair use you can easily shot holes into. Especially if the quotes are embedded in a much larger work (say, a biography).
>Summarising and paraphrasing what someone else wrote publicly is totally ok and legal.
It is, thankfully. The problem is that because of the ephemeral nature of digital media, it's quite possible for biographies to outlive their primary sources.[0] This means that a complete biography would need to include the actual article, if for no other reason than to preserve the original.
[0]: This is one of the reasons why the Internet Archives mission is so important.
The copyright status of forum posts probably means that they'll never be included in any book or work written this century except in the very limited form allowed by their authors. (Assuming that the current copyright ridiculousness is not quelled.) Which is too bad, as they're pretty interesting and I doubt their authors care so much unless you got rich off them.