People speak at conferences not for money but because they want to share knowledge, they love the atmosphere, they want to hang out with other speakers, they want to participate in an event and not pay for the ticket and travel, for self-promotion and to satisfy their own ego. Money is the last and least reason for speaking in public.
Also, I am wondering, if author’s startup uses any open-source software. It must be. Yes, some OSS is made by people on salaries in large corporations. But tons of software we use are built by people that want to help others. For free. May be again for self-promotion and to satisfy their ego, but, nevertheless, for free and to help others.
Just there two things mitigate all useful stuff that this article talks about, unfortunately.