Lichess, the gazillion of self-hosting software. There are many examples of free software that are exclusively (or let's say predominantly) used in noncommercial environments.

In any case, I agree with the commenter, and I think that developing a software which is also used by companies is different from looking for vulnerabilities in the context and scope of a bug bounty program for a specific company. Yes, you could argue that users of said company are going to be more secure, but it's evidence t like even in this case the company is the direct beneficiary.