License of GNU Emacs.
GPL in a nutshell
- Someone A create a recipe of beer. and publish it as GPL
- here is what another guy B can do, have to do
- B can make beer made with this recipe
- B can make money by selling beer made with the recipe
- B can improve the recipe, and publish it
- B can tell the recipe to others
- B can improve the recipe, but must publish it as GPL
- when someone C ask B, what the original recipe, B have to tell him
- when someone C ask B, what the improved recipe, B have to tell him
- in one sentence, when A create a recipe of beer, publish it as GPL, recipe and any improved recipe will be publicly accessable forever, and any one can make money by making and selling the beer and/or distributing the recipe.