Groupon is the daily deal websites that serves many major international markets, offering one coupon per day in each these markets. You can’t go anywhere online these days without spotting a Groupon ad. It's theory as we all know - the social features of its deep-discount offers for local merchants — a certain size group had to sign up in order for the deal to be “on” has been the reason for the huge success.
A free software license is a software license which grants recipients extensive rights to modify and redistribute, which would otherwise be prohibited by copyright law. To qualify as a free software license, the license must grant the rights described in The Free Software Definition or one of the similar definitions based on this.