I know its a spiritual successor to wonder boy, its even got a wonder boy anniversary mention on the box... they will get a lawsuit, WB license is still alive, they are making a remake of dragons trap. Its even got same characters (pepe, pig, snake, etc.)
Sega owns the "Wonder Boy" title, and since this title doesn't have Sega's involvement, that's why it's titled "Monster Boy" instead. But Sega doesn't own anything else. Everything else was owned by Westone, the creators of the series, which is why most of the Wonder Boy games came out on PC Engine under different titles. Westone went under a couple years ago, but the series creator still retains rights, and he's collaborating with the developer of Monster Boy. Everything about the project is on the up-and-up. He's also working with DotEmu, which is the publisher behind the Dragon's Trap remake.