Currently, it has hacks by myself, Cartmic, and Mr. Magius. It would be open to hacks by others assuming they were OK with it. It was originally associated with the Celadon Mansion forums that Cartmic and I were starting up, but then we merged with Twilight Hacking and PHO so now the wiki is just sort of there and not very attached to any active forum. So any hacks are welcome to be posted about and expanded on over there unless the author of the hack decides he/she doesn't want it posted there because of spoilers or something.
So far the main contributors have been myself and Cartmic.
I wouldn't have a problem with you copy and pasting your own stuff from another wiki, since it isn't like you can plagiarize yourself haha. But instead of putting the info for individual areas on the main Pokemon Christmas page, it would of course go under separate pages for the individual areas where it could be expanded into more detail (with the main Pokemon Christmas page being more of a general overview type thing like I have it now).
I haven't set up a template for it yet, but I was planning to have it so the pages for individual towns and areas had the data organized into collapsible sections separating it by which hack it was dealing with. That way when you go to the page for, let's say Azalea Town, you don't have info for Pokemon Brown, Pokemon Christmas, and Liquid Crystal all jumbled together. You could just expand the section for whichever hack you came there to look up.
* Will this wiki have only your hacks? Or will it have other hacks (such as Brown)?
* Are there other contributors?
* Can I just copy and paste the content for the Christmas hack from pokehacks.wikia.com and start from there? (Since I wrote the original article, I doubt this will be problem.)
In light of your interest in hacking wikis and the like, I thought you might be interested in something. A while back, I started my own wiki (along with Cartmic and a couple others) with the idea of thoroughly documenting our hacks in a way not unlike Bulbapedia. As of right now, it has generic summarizing entries for a few hacks, and the regions they take place in. But eventually its goal is to have pages for all the different locations, detailing the various things of interest that go on there, as well as pages for the different Pokemon as a reference for their changed evolutions, skill sets, and the like. Since you have already shown an interest in this sort of thing with the generic hacking wiki, I thought I would invite you to come and help contribute to the "MC Hacks Wiki" once the new version of Pokemon Christmas is released. Even the info I've put there is a little outdated, since I was trying to avoid spoilers by going into too much detail about the upcoming version before its release of course.