I too have tried to resist being negative, about the idea.
And I am certainly willing to make allowances for what might not be his first language leading to a poor description.
However, I believe the concept is flawed. Even the link he pointed us to has one skeptical scientific evaluation in the comments that show the problem. The spring you would need to get useful power would be like the ones on my truck and would take a few people standing on them to compress them. Hardly a pocket-sized device.
Sure there is energy stored in a compressed spring, but no amount of pulleys, levers and wishful thinking will get more energy out than was put in.
The problem is that many people won't understand this and they'll gladly shell out their $29.95 to get something that cannot live up to the marketing hype.
Caveat Emptor!
-brino