Mounting mini-pump on frame
The metal bracket is designed to fit the lugs of a water bottle cage.  If you have a bottle cage, the bracket goes between it and the frame. If you don't, it can just be mounted directly: the lugs on your frame will already have bolts in them, to stop the rain getting in. In either case, you might need or want to bend the bracket a bit, either to give more clearance for your bottle or to move the pump more within the frame. That shouldn't damage the bracket, as long as you don't bend it right back on itself or repeatedly bend it back and forth.

Mine lives on my down-tube. Unless it sticks out a long way, your legs shouldn't come close to it and, in any case, the pump will be between your legs and the bracket. If you're still worried about slicing your leg open, use a metal file to round off the edges and remove any burrs. Actually, that would probably be a good idea anyway to avoid hurting your fingers when you need to use the pump.