Regarding friendliness, both a bug tracker and the forum present a list of topics where you read/write messages and get notified when a topic is updated. So how does a forum differ in friendliness from a tracker? Sure, there are bad complicated trackers out there, but also very good ones (eg. the googlecode tracker).
But regardless of the difference in friendliness, the tracker serves a different purpose than a forum. The tracker is a coordination tool between developers, so that each contributor knows who's working on what at the moment, and along with a source versioning tool, also manages releases (i.e. which fixes are done in which version -- you also get a changelog for free).
For instance, I would like to contribute to tinycore myself, but I have no clue who is fixing what right now, and without source versioning and a bug tracker I have no way of finding that out. How would someone contribute code in absence of these basic coordination tools?
So initial question stands: are the tinycore devs interested in adding more devs to the project, i.e. opening up the development process? It's fine if they aren't, question answered, topic closed. But if they do, let's find out what is needed for this.