open source - Why do we have non-free software in the official repositories?

The Ubuntu wiki describes the "sections" of the official Ubuntu repositories as follows:

Main - Officially supported software.

Restricted - Supported software that
is not available under a completely
free license.

Universe - Community maintained
software, i.e. not officially
supported software.

Multiverse - Software that is not
free.

I thought that software in the Ubuntu repositories had to be open source, however doesn't the description of the Multiverse directly contradicts this?

The software in Multiverse is "gratis", but not free. These are some examples of cases in which software would be appropriate in Multiverse:

• The Software is not legal in every jurisdiction (DVD Decryption, ...)




• It's software-patent encumbered (MP3 Codecs, ...)




• It doesn't provide the user with all of the four essential Freedoms:

  
  
  
  
  
  1. Run the program for any purpose.
  
  
  2. Study how the program works, and change it to make it do what you want.
  
  
  
  3. Redistribute copies at will.
  
  
  4. Modify the program, and release modified versions.
  
  
  
  
  

  Note that those do not include a requirement that modified version be released with a license that grants the same freedom. This is called copyleft, and it's seperate from pure free software.




• There are issues with the licensing (like missing, unclear or invalid copyright notices)




• Any of the above is disputed or unclear

As htorque quotes, "The onus is on you to verify your rights to use this software ".

Note also: much of the software in Ubuntu enters the repositories through being in Debian first, so the Debian Social Contract & The Debian Free Software Guidelines are of some relevance.