Hello!

Could somebody explain me what's the difference between License for Wealth-lab Developer 6 and Key for it.
Which opportunities give me License in compare to Key?

A License is Key, basically.

However, in the context of the bulk purchase you're trying to arrange, there's a nuance important just for you. As I understand the context from your ticket, you're wondering whether the bulk could be split so that every participating member gets his own license. Basically, the answer is no due to our EULA, #1:

QUOTE:
Only you may use the Software. You agree that you will not assign, sublicense, transfer, pledge, lease, rent or share your rights under this License Agreement to any other party. (...)

It would be better to continue in the ticket (which appears to be closed prematurely by you). Anyway. If you're a group of individuals (let's say Tom, Dick and Harry), the head of the group gets the license and N Wealth-Lab 6 keys in a welcome letter. How do you share the keys between Tom, Dick and Harry is up to you.