--- type: "Glossary Term" title: "What Is Open Source Software (OSS)? | Roicool" description: "What does open source software mean? Learn what free access to source code really means, how it differs from closed source, and why businesses choose it." url: "https://www.roicool.com/en/glossary/open-source-software" lang: "en" dateModified: "2026-08-12" resource: "https://www.roicool.com/en/glossary/open-source-software" alternates: tr: "https://www.roicool.com/sozluk/acik-kaynak-yazilim.md" generated: { by: "process:roicool-cms", at: "2026-08-12T17:22:38.586Z" } related: - { title: "Software", resource: "https://www.roicool.com/en/services/custom-software-development.md" } - { title: "Glossary", resource: "https://www.roicool.com/en/glossary.md" } --- # What Is Open Source Software? Open source software is software whose source code is made available to everyone under a license, so anyone can freely view, inspect, modify and distribute it. In closed source software the code is the company's trade secret; here development is carried out by a worldwide community. WordPress, Linux, Android and Firefox are common examples, and for businesses the model makes a difference in cost, flexibility and vendor independence. ## In short In practice, open source software is defined by its license: permissive licenses such as MIT or Apache allow the code to be reused in closed products, while copyleft licenses such as the GPL require derivative work to stay open. Marketing teams rely on it daily, from websites built on WordPress to self-hosted tools like Matomo for analytics or n8n for automation. There is no license fee, but hosting, security updates and maintenance still belong in the total cost of ownership. ## Key points - With closed source software you can use the program but cannot access or change its source code; with open source the code is open to everyone. - Because the code is open, thousands of developers around the world continuously review the software and can find and fix security vulnerabilities. - There is usually no license fee; costs tend to come from optional support, setup and add-on services. - Support comes from community forums, online documentation and specialized professional companies; with closed source it is usually the vendor's official, paid service. - Vendor independence is a major advantage: even if the company behind it discontinues the product, open source software lives on and alternative developers can be found. - WordPress runs more than 40% of the world's websites; Linux is the foundation of servers, supercomputers and many smart devices. - Freedom to customize lets you adapt the software to your business's needs; with closed source you can only go as far as the vendor allows. Open Source Software (OSS) is a type of software whose source code is made publicly available through a license, so anyone can freely view, inspect, modify and distribute it. Let's think about it with a simple analogy: - Closed Source Software (e.g., Microsoft Windows, Adobe Photoshop): It's like a restaurant that serves a delicious meal. You can enjoy the food (use the program), but you're not allowed into the kitchen to see the chef's recipe (the source code) or change it. The recipe is the company's trade secret. - Open Source Software (e.g., WordPress, Linux): It's like a kitchen open to the community. There's a shared recipe book (the source code) that anyone can access. Anyone can take the recipe, adjust it to their own taste, improve it and even share their new version with others. This philosophy encourages collaboration, transparency and fast innovation in software development. Open source code means thousands of developers around the world can continuously review the software, find security vulnerabilities and add new features. That makes it both more secure and more dynamic. ## Open Source vs. Closed Source: The Key Differences To understand the value of open source software, it helps to know how it differs from the traditional closed source model. The core differences between the two show up in access, cost, development process and flexibility. ### With Open Source Software: - Access and Flexibility: The source code is open to everyone. This gives you full freedom to modify and customize the software to fit your needs. - Cost: There is usually no license fee, so it is free to use. Costs typically arise for optional support, setup or add-on services. - Development: It is continuously developed and improved collaboratively by a community of thousands of independent developers worldwide. - Support: Support usually comes through large community forums, online documentation and professional companies that specialize in the software. ### With Closed Source Software: - Access and Flexibility: The source code is the company's trade secret and is kept private. Customization is limited to what the vendor allows and the tools it provides. - Cost: You usually have to pay a one-time or recurring license fee to use the software. - Development: Development is carried out behind closed doors, only by the vendor's own team. - Support: Support is usually an official, paid service provided directly by the vendor. ## Popular Open Source Software We Use Every Day Open source software is everywhere in our digital lives, even if we don't notice it: - WordPress: The content management system that powers more than 40% of all websites in the world. Thanks to its flexibility it can become anything from a simple blog to a complex e-commerce site. - Linux: The operating system that underpins the world's servers, supercomputers and even many smart devices. - Android: The mobile operating system developed by Google and used on the vast majority of smartphones worldwide. - Mozilla Firefox: A popular open source web browser focused on security and privacy. - VLC Media Player: A versatile media player that can play almost any video and audio format. ## What Are the Advantages of Open Source Software for Businesses? There are many strategic reasons for a business to choose open source software: - Cost Advantage: The most obvious benefit. Instead of paying expensive license fees, you can download and use the software for free. This is a big advantage, especially for early-stage or budget-constrained businesses. - Flexibility and Customization: With closed source software, you're limited to the features the vendor offers. Open source software, on the other hand, can be completely modified and customized to your business's specific needs. - Security and Transparency: The "given enough eyeballs, all bugs are shallow" principle applies. Because the source code is public, thousands of developers worldwide constantly review it and can quickly find and fix potential vulnerabilities. You know exactly what's inside the code. - Vendor Independence: When you use closed source software, you depend on that company's future, pricing policy and support. If the company goes bankrupt or discontinues the product, you can be left stranded. With open source, the software lives on, and you can always find alternative developers or companies to support you. - Innovation and Speed: Because open source projects are constantly developed by a global talent pool, they can adopt the latest technologies and innovations much faster. ## Conclusion: The Power of Collaboration Open source software is not just a way of writing code; it is also a philosophy. Built on transparency, collaboration and the power of community, this philosophy has fundamentally changed the technology world over the last 30 years. Today's digital infrastructure largely stands on its shoulders. As a business owner or technology enthusiast, understanding the open source world doesn't just cut costs; it also opens the door to building more flexible, secure and innovative digital solutions. Whether it's a [web design](https://www.roicool.com/en/services/web-design-agency) project or a complex server infrastructure, open source is always a strong alternative worth considering. ## Related service - [Software](https://www.roicool.com/en/services/custom-software-development) Breadcrumb: [Home](https://www.roicool.com/en) › [Glossary](https://www.roicool.com/en/glossary) › What Is Open Source Software? Related pages: - [Glossary](https://www.roicool.com/en/glossary) Source: https://www.roicool.com/en/glossary/open-source-software · Last updated: 2026-08-12