Open source doesn't just mean access to the source code. The
distribution terms of open-source software must comply with the
1. Free Redistribution
The license shall not restrict any party from selling or giving
away the software as a component of an aggregate software distribution
containing programs from several different sources. The license shall
not require a royalty or other fee for such sale.
By constraining the license to require free redistribution, we
eliminate the temptation for licensors to throw away many long-term
gains to make short-term gains. If we didn't do this, there would be
lots of pressure for cooperators to defect.
2. Source Code
The program must include source code, and must allow distribution
in source code as well as compiled form. Where some form of a product
is not distributed with source code, there must be a well-publicized
means of obtaining the source code for no more than a reasonable
reproduction cost preferably, downloading via the Internet without
charge. The source code must be the preferred form in which a programmer
would modify the program. Deliberately obfuscated source code is not
allowed. Intermediate forms such as the output of a preprocessor or
translator are not allowed.
We require access to un-obfuscated source code because you can't evolve
programs without modifying them. Since our purpose is to make evolution
easy, we require that modification be made easy.
3. Derived Works
The license must allow modifications and derived works, and must
allow them to be distributed under the same terms as the license of the
The mere ability to read source isn't enough to support independent
peer review and rapid evolutionary selection. For rapid evolution to
happen, people need to be able to experiment with and redistribute
4. Integrity of The Author's Source Code
The license may restrict source-code from being distributed in modified form only
if the license allows the distribution of "patch files" with the source
code for the purpose of modifying the program at build time. The
license must explicitly permit distribution of software built from
modified source code. The license may require derived works to carry a
different name or version number from the original software.
Encouraging lots of improvement is a good thing, but users have a right
to know who is responsible for the software they are using. Authors and
maintainers have reciprocal right to know what they're being asked to
support and protect their reputations.
an open-source license must guarantee that source be readily available,
but may require that it be distributed as pristine base sources plus
patches. In this way, "unofficial" changes can be made available but
readily distinguished from the base source.
5. No Discrimination Against Persons or Groups
The license must not discriminate against any person or group of persons.