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class: center, middle

Software licensing and open source explained with cakes

  • Imagine you compose a recipe for a really tasty cake (a great idea).
  • In regular intervals you distribute cakes (release binaries).
  • Your family and friends love it.
  • But you can only bake so many.

(cake emoji licensed under CC-BY-SA-4.0, attribution: EmojiOne)

Possible outcomes 0/4: closed

Closed source (recipe never released)

  • Your cake is celebrated by The New Yorker magazine.
  • People will have difficulties to reproduce your celebrated recipe.
  • Nobody else will improve your recipe.
  • Bad copycats might appear, you don't get any credit.
  • Fewer tasty cakes will get consumed.

A friend tells you: why not distribute the recipe?

  • Put your recipe on GitHub.
  • Start the OpenCake organization.
  • Get feedback / start a mailing list.
  • More people will be able to enjoy the cake (.emph[increase impact]).
  • Maybe somebody will find ways to improve the recipe.
  • Everyone will know that it was your idea even though somebody else bakes it.

Mrs. X (running a famous restaurant) finds your cake recipe on GitHub

  • The chef tries it and it is great.
  • The chef suggests improvements (derivative work):

  • It becomes part of the restaurant menu.
  • Or does it? .emph[Depends on your license!]

Possible outcomes 1/4: custom

No license or custom license

  • No restaurant chef will touch it: too much hassle to employ a lawyer to be sure that the cake can be served to customers.
  • But maybe they will bake it and eat it and not distribute it and that is OK ("fair use" provision permits the making of copies for own use).

Possible outcomes 2/4: permissive

License: MIT or Apache or BSD-2

  • It is OK to use the recipe and sell the cake.
  • It is OK to not share the improved recipe.
  • If somebody becomes sick, it is not the fault of the OpenCake organization (limit of liability).
  • You may not get the improvements back to use yourself.

License: BSD-3

  • In addition to the above it is understood that the updated recipe are not endorsed by the OpenCake organization.

Possible outcomes 3/4: share-alike

License: GNU Lesser GPL (LGPL)

  • The famous restaurant has to share only the improved cake recipe but can keep the rest of the menu closed.
  • The restaurant guests have to be able to exchange the cake from the menu by improved cakes from other restaurants (dynamic relinking).

License: Mozilla Public License v2.0

  • Like LGPL but do not require that the modified cake can be exchanged by the restaurant guest.

Possible outcomes 4/4: viral

License: GNU GPL or GNU Affero GPL

  • If the cake is a part of the menu, the famous restaurant has to .emph[share the recipes of the entire menu].
  • You can use their improved recipe and improve it further:

  • Other restaurants can then reuse and improve the full menu and the hope is that we will all eat better food.
  • You support open restaurants. You can use everything they do, too.

What outcomes did we have?

1. Custom/closed

  • Derivative work typically not possible: others have to reimplement the wheel

2. Permissive

  • You may lose access to derivative work
  • Attractive for companies with proprietary software

3. Share-alike

  • You can reuse derivative work
  • Compatible with proprietary software

4. Viral

  • .emph[You always have access if someone improves and re-shares]
  • Not attractive for companies with proprietary software