This is an excerpt from my upcoming corporate open source strategy book, being published by Pragmatic Bookshelf in 2021. All book excerpt content is early in the development process and therefore unedited; the errors are mine alone (and will be fixed before publishing 😉).
The relationship between Free Software and Open Source can be pretty confusing at first, especially for business people who aren’t as accustomed to this world yet.
It’s important to recognise that, while these are two separate things, effectively they work the same for the user. If you have another look at the OSD, you’ll see that the Four Freedoms of the Free Software movement are represented there in the first four criteria. Open source shares the same genetic base code as Free Software and the two complement each other quite well for the most part, so much so that from a user perspective there often appears to be little practical difference between the two of them. They can download, install, and use the software; they can inspect, modify, and redistribute the code.
The differences are primarily cultural, which influence some practical matters. Supporters of Free Software believe that the goals of their movement—user and software freedom—require that the software always remain free/libre, including any modifications that might be redistributed. To accomplish this, Free Software is released under copyleft licenses that require that those modifications be released under licenses that will similarly ensure that freedom (you’ll learn more about this in the next chapter). Open source, on the other hand, is more permissive about such things. Much open source software can be modified and redistributed under completely different licenses (an uncommon and often complex process, but allowed under the license), including in some cases a license that closes the source code entirely. In that case, the software would cease to be open source and would become proprietary. Such a thing would be impossible in Free Software.
But again, in practice, you may not notice much difference between the two and they are highly complementary. This is why you see them combined in the FOSS (free and open source software) acronym: for the most part they can be treated as a single entity in conversation. That’s how they will be treated in this book, but never forget that they are different things. That knowledge will come in handy when engaging with the FOSS communities your company relies on or builds and manages themselves. Communities that identify as Free Software will have a different set of cultural expectations than those that identify as open source.
This difference may seem subtle, but it’s one that’s very important to some communities. Being aware of the distinction between Free Software and Open Source can help your company avoid cultural missteps when getting started in FOSS and leave a good first impression on the communities with which you engage.
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