Yeah, it's free. And it better be, not necessarily because it's a fan-game, but especially because Konami (RIP Hudson Soft) wouldn't like it if it was payable.
And yes, it is easy to download. I don't know if I'm allowed to post a link here but if you type "Power Bomberman download" on your search engine, it should come up quickly. It's on the BombermanBoard, a forum dedicated to Bomberman just like our own is with Lemmings. The game and its components are in a ZIP file, you just need to extract them in a folder and, here you go!
Also, the game got updated just today.