Osamu Tezuka, author of Jungle Emperor Leo, was a huge fan of Disney's work, and he was his main influence. Personally, I love to see this as a tribute rather than as plagiarism. And I'm saddened every time this story pops up, especially when it's framed like that.
Yes, I agree that the anal-retentive nature that these big firms go after copyright cases is reprehensible. And also that copyright law hinders as much creativity and progress as it supposedly serves to protect (especially the dumb shit supreme court decision that computer loading data from a CD into RAM falls is copyright infringement)...
But, technical point, the Joel Zimmerman thing is trademark law, and not copyright law. There is a big difference between the amount of original work and money Disney put into producing Lion King (with or without inspiration from Osamu Tezuka) and how much work it takes to draw 3 black circles in Illustrator and exporting as SVG. I mean, Lion King was based around the idea of "tell Hamlet with lions", which, as an idea, isn't even copyrightable. Combined with the original lines (in fact, even the language was different), original music, original songs, vastly different coloring, different camera angles, mostly different scenes, etc., it'd be a very hard case for any copyright lawyer to win in court.
That's not to say Disney's lawyers wouldn't try their hardest to prosecute if the tables were turned on them; they would and they did. But it's unfair to merely say Disney copyright lawyers are the scum of the earth, when the truth is closer to that all copyright lawyers (and judges) are the scum of the earth - that is, they all labor under what has become a terrible system of laws that, through a select few awful decisions, have come to oppress creativity in the interest of protecting existing corporation rather than foster improvement.
Just found a discussion on that topic on IMDB: http://www.imdb.com/title/tt0110357/board/thread/235177489 I hope that the discussion in this actual thread is not going to end like that :-)