We keep getting questions from users and customers who wonder why some premium features of free and open source software cost money. Comments even go as far as saying that this does not make it true open source software. With this article we want to summarize some basic ideas about free and open source software. 
What is free and open source software?
The terms “free software” and “open source software” are often used jointly. But let’s take a closer look at the exact definition and origin of each term.
Free software came first. It was originally described by Richard Stallman in the 1980s. The free software definition says: “Free software” means software that respects users’ freedom and community. Roughly, it means that the users have the freedom to run, copy, distribute, study, change and improve the software. Thus, “free software” is a matter of liberty, not price. To understand the concept, you should think of “free” as in “free speech,” not as in “free beer”.”
What is the difference between free software and open source software?
The terms “free software” and “open source software” as described above, refer to the same set of licenses and range of software programs. Nevertheless, both terms originally focus on different aspects of the software and have different underlying values.
Free software indicates that the software does not have any constraints on copyrights while open source software enables easy and effective collaboration on software development and distribution without any need for reverse engineering, as described in depth in Richard Stallman’s “Why Open Source Misses the Point of Free Software”. He explains that the open source software stands for different criteria than those of free software. Where one can say that all released free software source code is open source software, not all open source software is also free software, since their open source software licenses are too restrictive, e.g. not allowing to make a modification and using it privately, or missing copyleft.
Free software may also be referred to as “libre”. The term “freeware” in contrast refers to (also a proprietary software) that does not require payment for the basic use. Nevertheless, what makes it difficult for business models based on open source software is that free software is still being mixed up with freeware or even used interchangeably on many websites, posts or articles.
Paying for free and open source software
If you consider the above definitions, you now understand better why you may also pay money for free software. OpenProject falls into the definition of free and open source software. The source code is published on GitHub and is being continuously developed and improved by an active open source community; it considers the software freedoms. There is a set of engaged core OpenProject developers and product maintainers who also need to pay their bills. Therefore, we made parts of the software as premium features that need to be paid for. With this, you actively support the maintenance and further rapid development of the product.
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 Sources and further reading:
The definitions and concepts in this article are not new. I have summarized existing ideas. Here are the sources and further reading inspiration: What is free software?: https://www.gnu.org/philosophy/free-sw.en.html#f1 Free software: https://en.m.wikipedia.org/wiki/Free_software The Open Source Definition: https://opensource.org/osd Open source software: https://en.m.wikipedia.org/wiki/Open-source_software Why Open Source misses the point of Free Software: https://www.gnu.org/philosophy/open-source-misses-the-point.en.html