The open source definition from opensource.org defines open source software by the ability for the user to alter the software code. The definition states, "The program must include source code, and must allow distribution in source code as well as compiled form.... The source code must be the preferred form in which a programmer would modify the program." Programmers wishing to make open source software are bound by definition to open their code to users who can change the software. Furthermore, the programmer needs to use a familiar computer language. But the relationship between origonal programmer and user does not end.
A later section of the dfinition sates, "The license must allow modifications and derived works, and must allow them to be distributed under the same terms as the license of the original software." This means the origonal programmer needs to create a forum where users can publish their alterations to the origonal software and the open source license covers the alterations.
If a software is open source, it fits the criteria under the open source definition, and it is, therefore, legal for users to edit and publish their own versions of the software under the same open source license. It is illegal, however, to edit open source software and sell the edited version. The edited version of the software is covered by the origonal version's license which, again by definition, must be distributed freely.
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