My understanding of copyright laws is that they only apply when the term is being used in the same space as another copyright. So if I made another cartoon character named tigger that would be illegal, but creating something completely separate (especially something like OS software where I'm not really selling anything) the copyright doesn't really apply. I'm gathering from HN that this is an incorrect interpretation, can anyone explain it to me?

Consider: even if your interpretation were legally correct, what matters is your ability to convince a court to say so when Disney sues you.

That's probably an enormous expense that you'd be better off avoiding altogether by changing the name. Rebranding is also a lot easier now than once you've grown large enough to have shown up on Disney's radar.

You probably can't afford to be right, their lawyers however can afford to be wrong.

Disney has sued pre-schools/kindergardens for putting up their characters on the walls. Think about that.

You're thinking of trademarks, not copyright.

If it has potential to cause customer confusion, it might be a trademark violation. A company is required to defend their trademarked terms, otherwise they may become generic terms.

(Standard I Am Not a Lawyer disclaimer. Go talk to a real one if you're worried.)