Not a very catchy title.
Citizendium is a completely separate project from Wikipedia - but. It calls itself a "progressive fork", which means it sucks information from Wikipedia, then forks away. It's been set up by a former Wikipedia Editor-in-Chief, Larry Sanger.
Why? Response to the criticism (including from Citi's initiators) that Wikipedia is too free in its allowance of anybody to edit it. In contrast, Citizendium looks like it allows only named/registered users to add content, and it maintains a group of editors to oversee that content. It regularly refreshes from Wikipedia - where there is no Citi change.
Its thesis is that people will gravitate to it both to add content and to read it, as people appreciate its greater reliability.
I'm giving it oxygen, but I'm not 100% convinced, for several reasons:
1) It restricts the adding of content, compared to Wikipedia;
2) ...yet it will propagate what it sees as Wikipedia's errors;
3) Wikis in general work best when they reach a critical mass. Wikipedia's there now, but many other wikis aren't (eg ITToolbox: has a lot of good tech blogs, and attracts unofficial technical support from a number of vendors, yet their wiki effort is a dismal failure so far). It's hard to see people gravitate away from Wikipedia. (But it's certainly possible, if the product is good enough. That's what happened to google over Altavista, which used to be the top search engine.)
4) The differences between the wiki models is a bit subtle for most people, who are only looking for something consistent and reliable.
5) Wikis are a real balancing act, between freedom to add content, and the checks in place on that freedom. How many people will agree that removing the power of anonymous authorship will improve content by this much while reducing additions by only that much?
6) It could be just a grudge project. However, a fair bit of effort seems to have been put into it so far. Yet two managing editors have been announced so far, but each of them in turn pulled out.
8) It's not up. Yet. It says it plans to be up by the end of the year.
Still, the internet is a great democracy for ideas.