"All Linux distributions are supposed to be free, but some
distributions are freer than others. Because some gaps remain in
free software functionality, many distributions, including Ubuntu,
include proprietary applications, such as Acrobat and Flash
readers, and drivers for video and wireless cards. Many more
include Linux kernels with proprietary firmware for device
drivers.
"Among the hundreds of distributions, only eight are officially
recognized by the Free Software Foundation as being completely free
of proprietary material.
"Mostly based on Debian or Ubuntu, and often South American or
Spanish in origin, these distros often lag behind the most popular
ones in the software they include. Sometimes, too, they lag in
functionality -- for instance, they include the Gnash Flash-player,
which is still not a complete replacement for Adobe's Flash
player."