I believe in open source as a form of sharing, networking between companies and training between developers.
With open source, developers from all over the world collaborate on shared projects.
Open source software is software with source code that anyone can inspect, review, modify, and enhance.
Open source software is a great way to learn new technologies, to share knowledge and to collaborate with other developers.
Building a project using open source software is building it on top of the shoulders of thousands of developers. You get efforts on the subject from all over the world for free, and you can contribute back to the community by sharing your own code.
Furthermore, open source software is often more secure than proprietary software, since tons of developers can review the code. This also enhance privacy and transparency.