There is a tremendous amount of free software that runs the worlds infrastructure.
Programming languages, compilers, libraries, frameworks, text editors, databases, operating systems, utilities, servers, encryption, and even curl all lower the price of entry for everyone to contribute and innovate, even when they’re using free tools for commercial purposes.
The article's point is that the reason curl is so widely used by almost everything is because it's free and has a open source license. If it requires some small amount of money per commercial install, or even if it had some license terms that weren't appealing to legal teams at these companies, it would likely not have the widespread adoption is currently has. If every piece of curl-like software in the space were pay-per-install, these companies probably would go and use one of them, but if just one of the offerings is free for all use it's going to top the paid offerings most of the time.
ummm, the gist of it is, someone else have to write for free, else every time you curl you would be paying $$ to oracle or someone :|