So if one wants to open-source his project and sell it :

- Licence as AGPL

- Mention that commercial use (without having to open source the derivative work) is available

Did I get it right?

1- Is this solution useful for subscription-based contract too?

2- Does it make a difference if the product is a app, library or hardware device?

> Did I get it right?

I think so.

> 1- Is this solution useful for subscription-based contract too?

If you mean SaaS, then maybe. I emailed Stallman about the ethics of the SaaS case and he said it's a net good.

You might want to think about whether the license actually gives you leverage in that case though. You might find that the corporations are perfectly willing to host a service using your AGPLv3 software. That's within their rights.

You only gain leverage if they want to create a proprietary version of your software.

> 2- Does it make a difference if the product is a app, library or hardware device?

Absolutely. The GPL has very specific wording with regards to linking and distribution which trigger license conditions. You should read the full license for a better understanding.

Hardware is a completely different matter, I won't even pretend to know anything about how licensing works in that case.

Remember, I'm not a lawyer. I'm just a hobbyist free software developer who's also trying his best to understand all this and make the best possible decision.

The main problem is that you need to have contributors sign a copyright assignment/CLA, otherwise their code is going to be AGPL only and you cannot license it commercially.

Or you don't have any contributors, which is the base case, I guess.