I could be wrong here, but I'm pretty sure it's a-okay for you to use your own writing somewhere else. In fact, a lot of people like R Ranson and Paul Wheaton and likely others have used permies as a kind of scratch pad and then taking their writing here and turned it into a book.
In fact, Paul pretty much gives the okay for it in
this thread on residual income streams
paul wheaton wrote:815: every time something makes you angry, write a permaculture solution into a blog or permies.com post. After a year, massage all that into an ebook (my book has now sold more than 20,000 copies).
I think it would be awesome to have a link to permies in your article!