D20 is a fair quality host. Reasonably lightweight, solid, overall well built. Very good for the price.
Do note that D20 is not fully waterproof. And the lens is not great…but better than the only Led Lenser that I’ve seen so far.
In Boruit Headlamp Review D10 (aka. EHL0628) - King of the Budget Headlamps? there’s a lot of discussion about D10 / D20 / D25 family of lights…though mostly about D10.
Here’s a review:
Ultimate Headlamp Review Comparison!
Do note that there are differences between seemingly identical lights:
- some are glued, others are not
- some have headbands with weak holders. They don’t hold the flashlight securely. Seek the ones which have a nub in the middle:
UI can be improved, Quadrupel offers custom drivers which are compatible with Andruil.
As to the legalese…I can’t give you a quality answer so I won’t even try. Maybe other members will help, if not - study the subject yourself or ask a technically-competent lawyer.