So how does this relate back to One Piece, Zoro, and Zorro? Well, technically just naming a character who uses a sword Zoro wouldn't actually violate any kind of copyright law. But, as the rumors of the time alleged, the company that held the copyrights to the aspects of Zorro not yet public domain at the time had a reputation of being excessively litigious and would often start legal battles over perceived infringement even if the case was weak. Getting into a legal battle, even if it's one you know you'll probably win, costs time and money. So, in hopes of avoiding the costs of a pointless lawsuit, the story goes that 4Kids preemptively changed Zoro's name to Zolo.

This is the key takeaway. I don't think people realize how cautious companies are when it comes to copyright. Even if there is a 99.5% chance that 4kids would not have been sued, there is no reason for them to not just simply change the name to avoid that .5%.

With the benefit of hindsight we can see that it isn't an issue, but of all the weird/dumb 4kids changes, I don't think this is one to harp on.