I would recommend a much higher threshold than 'three people'.
In the abscence of an ISO code, I think there needs to be an actual community of some size, as evidenced by publications, conventions, websites, mailing lists, and other things of that nature. I think there also needs to be a showing of actual interest from more than just one or two people.
Is disk space really so expensive that we need to be so strict with conlangs? If they are not very big, they are not going to take much disk space anyway.
Additionally, the argument about there being few changes on Toki Pona is flawed. The Toki Pona Wikipedia is more active than the Swahili Wikipedia, and has probably more useful information on it as well (the majority of articles on the Swahili Wikipedia are entries of a Swahili-English dictionary, not what Wikipedia should really be there for). But that doesn't imply that we should delete the Swahili Wikipedia.
Rather, I propose to allow any conlang that is actually used for communication. Three people knowing it well, and a few others understanding it a bit, can be enough for this.
Marcos.