In the case of sqlite (created by D. Richard Hipp) the software is public domain. Development was funded (at least in part) by corporations. The author isn't ex

In the case of sqlite (created by D. Richard Hipp) the software is public domain. Development was funded (at least in part) by corporations. The author isn't expecting payments from "ordinary" users. The author's firm charges hefty fees for consulting services. These are directed at enterprises needing "certified" versions of sqlite. I'm assuming these are companies providing software under military/government contract. So it's an interesting strategy: release sqlite as public domain. The software is used everywhere, so much so it's an indispensable part of the infrastructure. Then when giant enterprise uses it charge huge fees they gladly pay. Hipp is without doubt a genuine genius.