4.2.1. Licensing Models

• GPL guarantees the following freedoms (as in free speech, not free beer)
  1. You can run the program as you wish for any purpose
  2. You can study the source code and change it to do what you want
  3. You can make copies and distribute them
  4. You can distribute modified versions

• Derivative work inherits license (mistermed virus nature of GPL)

• Linking is considered derivative work in GPL but not in Lesser GNU Public License (LGPL)
  -> GNU libc is most prominent LGPLd program

• "Open Source" licenses usually omit the fourth freedom from list above (Mozilla license MPL)

• BSD style licenses have no such derivative work clause and thus cannot prevent "misuse" of software (OpenBSD, FreeBSD, NetBSD)

• Because of so many licenses all dubbed "open source", check which freedoms they really entail