The license says use it however you want with nothing in return. They usually get nothing in return. It's a license best used when you want maximum uptake by us

The license says use it however you want with nothing in return. They usually get nothing in return. It's a license best used when you want maximum uptake by users, including proprietary products. It's also good for people who enjoy knowing others enjoy using what they build. Whereas, it's one of the worst licenses if a supplier wants money. Lets assume goals like OpenBSD's. If one also wants money, they can make the software paid, free for many categories of users, source-available, and derivatives (mods) allowed. The paid part can be regular payments or one-time per release. Probably an exception to mods allowed saying they can't backport paid features from new versions to old versions but independent creation is allowed. From there, companies will pay to support it or they'll determine it has no market value. There are proprietary, source-available RTOS's on the market for real-time and secure use. One source said, but I haven't verified, that INTEGRITY RTOS royalty-free was around $17,000 minimum per product or company. Another said LynxOS with communications middleware was around $50,000. A number of small vendors exist showing one can generate sales if their product is marketable. Tons of companies selling firewalls, load balancers, etc like OpenBSD is often used in. https://en.wikipedia.org/wiki/Comparison_of_real-time_operating_systems https://en.wikipedia.org/wiki/Comparison_of_real-time_operat... So, if money is important, they can change their terms to demand money some or all of the time. If the license says "free giveaway!," expect most people to treat it that way. I imagine quite a few of the developers have exactly that expectation. They are motivated by the joy of writing great code, not money.