Keyword: Free Software Licences

• Licenses express the rights of the copyright holder

  • Govern under which conditions someone may do something with the software

    Proprietary software also uses licenses

  • Especially: Use, modify, distribute

  • Software licenses are based on copyright

    Copyright is based on state power

  • Rights or restrictions beyond copyright need contracts

• The genius hack: Use the copyright system against itself

  • Copyright creates scarcity by denying rights
  • Copyleft creates abundance by granting rights

• Two main license types: GPL and BSD

  • Though many licenses exist

    Since a license is a contract it's easy to invent a new license

    But it's rarely useful

  • Lists of Free Software licenses by FSF and OSI

• Main difference: May a licensee close sources again or not?

  • BSD: Software may be distributed without sources
  • GPL: Sources must be kept open
  • More than 50% of Free Software projects use the GPL

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