When you hear the term “open source,” it’s talking about any publicly accessible design that people are free to change and share as they please. It started with software development, with code that anyone could view, modify, and distribute, but it has since grown to become a model for a much broader philosophy: One that promotes collaboration and innovation across all sorts of different fields.

Strictly in terms of software, “open source” is any program with freely available source code, the underlying instructions that tell a program how to function. Programmers can view and adjust this code to do whatever they want, whether it be to improve the software’s functionality, fix any bugs, or transform it for entirely new uses. It’s the opposite of proprietary (or “closed source”) software, such as Microsoft, Adobe, or Google products, where the code is controlled entirely by its creator(s).

Licenses are the driving force behind open source. They’re what give the public legal permission to use the software for whatever purpose they want, plus the freedom to share their modifications with others. Granted, these licenses do sometimes come with the promise that you release your altered code as well. It’s a principle known as “copyleft,” and it’s a way to keep the collaborative spirit alive. That way, programmers can build on each other’s work and strengthen the open source ecosystem as a whole.

The concept of open source dates back to the 1950s and 1960s, when researchers were working on the telecommunications networks that came before the modern internet. Known as the Advanced Research Projects Agency Network (ARPANET), the researchers behind it openly shared their code and findings with each other to make better projects. Collaboration and peer review meant everything to their research, and it helped establish the values that still define open source to this day.

By the 1980s, “open source” had started becoming a full-fledged, organized movement. At the time, it was called the “free software” movement, and it was built on the principle that software should respect the users’ freedom to do what they wanted with its code. But, unsurprisingly, the term “free software” led to some confusion because the name implies software that’s free of cost, but its intended meaning was software that was free of use.

By the late 1990s, the concept of “open source” had taken over the momentum from “free software.” Around that same time, Netscape released the source code for its Mozilla browser as open source. This led to Mozilla (and, later, Firefox) being embraced by the corporate world and beyond. That same year, the Open Source Initiative (OSI) was founded. It formally defined and promoted the concept and focused on practical, business-friendly ways for people to benefit from it. After all, “free software” doesn’t sound like a big money-maker, does it?

Linux is one of the most famous open source projects in history. It came about during the OSI movement and has since become the foundation for countless web servers, mobile devices, and even entire cloud infrastructures. The internet itself runs on open technologies like the Linux operating system and the Apache web server. The cloud computing platforms behind streaming services and collaborative online workspaces are another example of just how much of a role open source plays in the digital services we use every day.

Today, open source has gone far beyond just software. Its influence can be seen in the fields of science, academics, law, health, politics, and countless other fields using open models to speed up progress and innovation. But remember: open source is not the same as saying “free of charge.” Developers can still sell open source software or offer paid services around it, such as support, customization, or training… all while still falling under the definition of open source.

Going open source has its pros and cons, but its flexibility has actually led to hybrid models where companies combine open-source platforms with their own proprietary products to create something uniquely their own.