"Arguably, the prime reason why developers tend to opt for open
source licenses is that it lets their software roll on as a group
or community exercise, and this in turn enhances productivity
manifolds. For instance, Acquia Network, the parent organization
behind Drupal, currently consists of 160 employees. Obviously, a
company of that size cannot sustain a mammoth project such as
Drupal. However, Drupal itself being open source, is helped by the
numerous volunteers from the community. Similarly, WordPress rides
the wagon of a super-active community while its parent
organization, Automattic, concentrates on select issues.
"Open source licenses nowadays come in multiple versions.
Wikipedia has a rather incomplete list of some of the major free
licenses at http://en.wikipedia.org/wiki/Free_software_license
While all such licenses cater to diverse purposes with the same
goal ('freedom'), we shall restrict ourselves to only the major
ones for the sake of simplicity. From a small/medium enterprise's
point of view, the noteworthy licenses include GPL/LGPL, MPL,
Apache License and BSD License."