Angels Dancing on Heads of Pins

And Schibler with others, maketh the difference of extension to be this, that Angels can contract their whole substance into one part of space, and therefore have not partes extra partes. Whereupon it is that the Schoolmen have questioned how many Angels may fit upon the point of a Needle?

Licenses: Who Reads Them?

• Todd announced the Wifi instructions yesterday:
  • Set your ESSID to POSSCON
  • … then agree to the terms.
• By show of hands: how many of you read those terms?

Licenses: Who Reads Them?

• Well, I read them.

• But did you do any work yesterday?
  • And do you work at a for-profit company?
  • Not clear to me that was permitted.
• What permissions you have matter!
  • … while this is a “toy” example.
  • … but many licenses you agree to have serious consequences.

What the License Says Matters

Why Use This System?

• Many software freedom advocates disagree with the concept of software licensing.

• So why do we use such things?

Why Do We Need Licenses?

• Software is governed by copyright …
  • … since it’s expression fixed in a tangible medium.

• Only way to give rights to users is to grant a copyright license.

• What rights do you get?

Ye Ol’ Four Freedoms

• to use.

• to learn and modify for yourself.

• to copy and share.

• to modify and share modified versions.

What a Free Software License Does?

• Copyright on software governs three basic activities:
  • copying, modifying and distributing.

• By default, you’re prohibited from doing those things.

• A license is:
  • a document that gives you permissions …
  • … that you otherwise wouldn’t have.
• A software freedom license, first and foremost:
  • assert recipient’s to copy, share, modify and redistribute the software.

How Do I Know?

• There are (unfortunately) a lot of Open Source / Free Software licenses.

• Fortunately, there are two authorities:
  • Free Software Foundation’s List of GPL-Compatible Free Software Licenses
  • Open Source Initiative’s Open Source License List

• Easy rule: feel pretty safe with any license that’s on both lists.

• But there are more policy issues to consider.

Did You File Your 1040 Today?

• Some people find software licensing a boring topic:
  • but most people find the USA tax code even more boring.
• I find both fascinating:
  • Ultimately, these codes implement policy.

Tax Policy

• What Is a Tax Write-Off?
  • It’s a government incentive to encourage certain behavior.
• What Is a Tax Penalty?
  • It’s a government incentive to discourage certain behavior.

• We can argue what the right policies are.

• But understanding them is a rote application of this principle.

Licensing Policy

• Licensing policy works somewhat like any other policy (e.g., tax code) incentive/discouragement structures.

• Typically, a software freedom / open source license:
  • permits on behavior it seeks to encourage.
  • places extra requirements for behavior it seeks to discourage.

The Simplest Free Software License

• ISC License (w/out warranty disclaimer)

Does/Should a License Do More?

• Ultimately depends on the authors’ goal.
  • More on this in a moment.

• Every Free Software license gives first recipient those four freedoms.

• Question is: What about everyone else?

Basics of Copyleft Licensing

• Concept: share and share alike.

• Accomplished via copyright requirements:
  • distribution accompanied with complete, corresponding source.
  • distribution of modified versions need same (with changes).
• Generally triggered on distribution:
  • (Note: Affero GPL triggers on modification.)

Other Policy and Rules?

• Warranty disclaimers.

• Patent policy.

• Attribution requirements.

Comparing Licenses

Meta-License Policy

• inbound=outbound
  • Your hold copyright on your own contributions.
  • You offer those changes under the project’s license.
• Other arrangements
  • CLAs, ©AAs, and many others.
  • These are common, but create inequality.
• If the license is good enough for the project, it should be good enough for contributions.

A Final Example

• How many Mac users are in the room?

• How many GNU/Linux users?

Does Free Software Remain Free?

• Both Macs and GNU/Linux are based on Free Software.

• Macs are based on BSD, but Apple modified and made it proprietary.

• Linux is GPL’d, so policy prohibits proprietary modifications.

More Info / Talk License

• URLs / Social Networking / Email:
  • Copyleft and the GNU General Public License: A Comprehensive Tutorial is available and welcomes contribution at copyleft.org.
  • Conservancy: sfconservancy.org & @conservancy
  • Me: faif.us & ebb.org/bkuhn
  • Slides: ebb.org/bkuhn/talks & gitorious.org/bkuhn/talks (source)
  • SUPPORT Conservancy: sfconservancy.org/supporter/