4. Standard Linux Base  The vast number of different Linux
distributions, while providing lots of healthy choice for Linux
users, has created a problem for software
developers—particularly developers of non-free software.   To
help overcome this problem, a new project sprang up called the
“Linux Standard Base.” It aims to describe a standard base
distribution that complying distributions will use. If a
developer designs an application to work against the standard
base platform, the application will work, and be portable to,
any complying Linux distribution.  You can find information on
the status of the Linux Standard Base project at its home web
site at http://www.linuxbase.org/.