OpenSource means the SourceCode to the software is available.

It often refers to Software released under the GPL or a similar license, and thus overlaps with the "FreeSoftware" term. However, the two should not be confused, as OpenSource software may be non-Free, even non-free. Examples include commercial versions of Unix or Java, of which the SourceCode is available, but third parties are not allowed to distribute it.

DebianLinux has a "nonfree" section for software that the project may legally distribute but which does not meet the project's definition of FreeSoftware. This includes many OpenSource programs.

Compare Free and FreeSoftware.