Copyleft

• Copyleft licenses force redistribution in the same or similar terms
  • software remains free even if modified or incorporated
  • private or internal modification does not mandate distribution
  • any price, or none, can be demanded for distribution
  • derived works may become a thorny issue
• Non-copyleft licenses give the maximum freedom
  • no problems ever with derived works or linking or reusage
  • software can be redistributed in different terms
  • maximum incentives to diffusion, useful for diffusing a standard
  • few requirements from the recipient