can this helmet be used for skateboarding and/or mtn biking? is it certified for those uses?

I wouldn't. BD makes this helmet for climbing. The foam and padding is completely different for skateboarding lids. Think of it like using a kayak lid for your motorcycle, it will work but the idea of a helmet is to keep you safe, not just to show the cop your wearing a helmet to avoid a ticket. Having 5 different helmets for 5 different sports isn't the worst thing, remember its all about the safety.

You could use it for those things but it is not certifed for those activities. I think the BD helmets were designed by someone from the bike helmet world, but they do have different protection intentions than biking or skating. In short, yes it would work, but the company hasn't paid to have it tested to other industry standards.