Hi Jan, I also received an invitation on Twitter to join them as an online writer. I actually thought it was a paid content writing job. I queried it and they said they would provide details, which they did. They provide you with two key words which you have to use in the title of your articles and they must be over 700 words etc and to stay an active member you are required to submit two new articles per month.
Nothing was mentioned of monetary compensation, just that you could have an author bio and exposure through their site. Which doesn't sound very generous for the time you would spend writing the articles, stories etc.One stipulation is that it ha to be original work by you the author and no part can be plagiarized.
I did however have two articles that already suited their keywords but they had been parts of hubs I had already published. I removed sections, changed wording and titles to suit, added extra content and submitted it to see what happened.
They emailed back saying the article was high quality but parts were already published on the web, so they couldn't accept it.
Sounds like it would be too much effort for me if there is no payment incentive.