Rise April and Edsel from "Mage"
 

What's the saying: "If you want to make a completely original idea you must first reinvent the universe."

Never knew about this comic. If it's intentional then the answer is pretty simple, they had the rights to April but not Edsel.

To be fair, "black girl holding a baseball bat" is probably something you can find in hundreds of shows, books, movies, etc.

Sure, though a magical glowing green bat... now that's an interesting coincidence if that's all it is.

It's almost like people pay homage to the stuff that inspires them. TMNT is pretty much known for concept recycling.

Perfectly fair. The original concept of TMNT followed the example of Cerberus the Aardvark and similar indy comic anthropomorphs, pay homage to the works of Frank Miller like Ronin and Daredevil and poke fun and Teen Titans and kiddie super hero teams in general.