Sure! IANAL, just a dev, but my understanding from seeing this play out over the last 20 years is the following broken down first by public vs. private benefit:

Sure! IANAL, just a dev, but my understanding from seeing this play out over the last 20 years is the following broken down first by public vs. private benefit: 501(c)(3): Organizations under this classification must primarily serve a public interest and not a private interest. Any private benefit must be insubstantial. 501(c)(6): These organizations are designed to serve the private interests of their members, as long as those interests align with the broader industry or line of business. Everything else follows from this distinction IMHO. You see it play out in the Linux or Rust foundation, in contrast to the Python or Zig software foundation. It's easier to get attention and members with a trade organization, but over time, over the long term, there's a stark difference that I believe is not disputed.