a license is a way for software manufacturers to make sure that bootleg software is not supported. You must have a license(for businesses) to run certain software. This applies when you have say...
By purchasing a site license, a company can obtain the right to use multiple copies of software, which is a popular way for companies to provide software to employees.
irrevocable is the license which cannot be recalled or used again in the future such a license is provided to a single user and this user cannot share this license with someone else
I'm not sure what you're asking here. A perpetual software license is a software license agreement that has an "infinite" term, does not expire, or in some cases, automatically renews itself, if so...