• Software is usually generally copyrighted,
  independent of its functionality.
• Licenses transfer rights to use the software
  from the author to a (potential) user.
• Unclear licensing is a huge problem
  for using and developing software.
• There are a number of licenses for (free) software
  that were developed particulary for open source.
• Every program with (potentially) more than one user\\ should have a clear license.

Open Source Licenses
Overview of different open source licenses from the open source initiative