Glossary - General Descriptions of Certain Open Source Related Terms:

See also Validos frequently asked questions about open source software.

Term: Copyleft

A copyleft clause in software license stipulates that in case of redistribution or relicensing, any changes made to the software have to be licensed under the same conditions as the original software. All open source licenses do not have copyleft clauses, and there are several types of copyleft clauses. Copyleft clauses can be categorized into e.g. weak and strong copyleft depending on the circumstances in which the conditions must be followed (strong clauses must be followed in more numerous circumstances). The best known license including a copyleft clause is the GNU General Public License 2 or GPL 2.

Typically, a copyleft clause is applied when the original software is redistributed. In order to have a right to distribute the original software with modifications, the distributor must distribute the modifications under the same conditions as the original software.

Copyleft clause is often (erroneously) assumed to have an automatic effect that can lead to "contamination", i.e., that any software combined with copyleft licensed software could somehow be transformed to be licensed under a copyleft license. However, this kind of mechanism is not written into any known license. The result from not following the clause is a copyright infringement and/or possibly penal sanctions.

Example: Mozilla Public License 1.1 or MPL 1.1embodies a so-called weak copyleft clause. According to the clause, if files in the software distribution are modified, the modifications must also be licensed under the MPL license. Failing that, the original software may not be distributed with the modifications. The modifying can also be performed by, for example, copying a file or part of a file into another, self-made file.

Synonyms: reciprocity, viral effect, hereditary effect.


Term: License (Software License)

Software license refers a permit to utilize a software, i.e., the conditions according to which the software may be utilized. A license may be construed as an agreement between the holder of the rights to the software and the utilizer of the software (this is the predominant case under Finnish law) or as another type of permission (in some countries, the license / permit to utilize is governed by different legal rules than a contract). Open source software is licensed under so-called open source licenses.

Example: Apache 2.0 is a license. It has been created by Apache Software Foundation (an American foundation)  and it is used as a license for the software projects of the foundation, as well as more widely elsewhere. If one wishes to use Apache 2.0 licensed software one must obey the conditions of Apache 2.0.


Term: Permissive License

So-called permissive open source licenses give a permission to use the software without major restrictions. The conditions usually relate only to maintaining and publishing the copyright and license information. These licenses enable modification and distribution of the software also as a part of a commercial software under a proprietary license. Common permissive licenses are BSD and MIT License along with their different variations.

Synonym: academic license


Term: Source Code

Source code is computer code written by a human (programmer). Before source code can be run in a computer it must be compiled or interpreted into a form of code a computer can understand (e.g. binary code).  Source code is needed to e.g. develop, modify or patch a software program.


Term: Open Source Software

Open source software is software that is published under a so-called open source software license. Conditions of this type of software allow copying, modification and redistribution of the software quite freely. Open Source Initiative (OSI) maintains a definition of open source software. Free Software Foundation (FSF) uses the concept ”free software” which means, from a commercial user's viewpoint, much the same thing.

Additionally terms OS, OSS, FOSS, FLOSS are used. They mean pretty much the same thing. FLOSS = Free and Libre and Open Source Software.

Synonym:  free software


Term: Fossology

Fossology is a tool running on a Linux platform for examining software source code. Fossology was originally developed by HP for its internal use and now it is developed as an open source project supported by the Linux Foundation ( Fossology identifies several hundreds of licenses and license clauses and variations of those. Validos uses Fossology as a tool for examining source code.


Term: Intellectual Property Rights

Intellectual property rights usually refer to the protection of the results of creative work and/or commercial investment. Typical forms of protection are copyright, design, trademark and patent. The most common form of software protection is copyright. Open source licensing is based on reserving the copyright to the author and subsequently giving a broad license to the user of the code.

Right to a trademark can protect a trademark of the software or similar. A patent can protect a technical invention implemented in software. Patenting computer programs or algorithms is more common in United States, Australia and Japan, but now increasingly possible also in Europe.

Synonyms: IPR (intellectual property rights)


Termi: Public Domain

Using a public domain (PD) notice, an authors can relinquish their copyright and place their works into entirely free use of the public (i.e. into so-called public domain). Public domain software must not be confused with open source software where licensing is based on the permit to use granted by the owner of the copyright.


Term: Freeware, Shareware

Freeware is software which can be loaded and utilized without license payment. Freeware licenses are usually proprietary-type licenses. Shareware is usually in all respects similar to freeware except a fee is required in one way or another in order to use the software (usually a free trial period is included). Freeware or shareware do not mean the same as open source.


Term: Commercial Use, Use in Businesses

Commercial use of a software is a vague term. All use by a company can be seen as commercial use (broad definition) or, alternatively,  just copying and distributing a copy for a fee (limited definition). There are numerous possibilities between these extreme cases. At Validos, we use the term "used in businesses" which covers all conceivable use of software by a company.