I don't know if that includes fanfics or articles on things like Freespace 3/Freespace 3 and Derek Smart.
It doesn't. We can deal with fan fics later. As for the other two, no one is ever going to think Derek Smart is an alien entity who showed up in the game and started wiping out Shivans and Terrans alike with his alpha male field. We don't run the risk of anyone thinking that it's canon to the FS universe.
As for FS3 the same sort of thing applies as long as some damn fool doesn't come along and start adding what would have happened in FS3 (Well apart from the comments by

as those are canon to FS3).
If I were to restart this thread I'd ask this question.
Should we allow fan speculation on the FS universe in the wiki which isn't tied to a specific campaign or campaigns?
1) Yes but only on a fan speculation page
2) Yes but only with adequate criticism of any flaws in the speculation.
3) No - Fan speculation should be listed under a campaign which supports it.
I'd then clarify a few things right at the start by pointing out the possible drawbacks I can see with any of those methods.
1) Easy to end up with the appearance that the fan speculation page is an attempt to set up an extended canon
2) Potential of ending up with an edit war.
3) I'll let WMC figure out what the drawback to this one is.