Just like Qt does it.

You don't want to pay upstream for their work? Use GPL license and get as much money as you are willing to give them.

Otherwise use it in a commercial setting, you need to pay for the commercial license instead.

It is not much different from the demo versions of shareware days, and yes even in those days you could get the source in some products.

You offer a copyleft license like AGPL but also offer a paid license for those who don't want to deal with AGPL. Since you as the creator own the copyright, you can license it however you want, including multiple licenses simultaneously.

It's a pattern that works very well - many large companies have standing policies that they can't use copyleft licensed software so they have to get the paid license while those happy with the copyleft social contract get to enjoy and contribute for free.

Correct, although not every company shies away from copyleft, namely Amazon which will package your AGPL product wholesale and sell it. They are after all not required to open source their infrastructure code.

> package your AGPL product wholesale and sell it.

if anyone has a problem with that, then they have a problem with software being open source.

Or they are discriminatory and just don't want anyone they personally dont like to benefit.

> Or they are discriminatory and just don't want anyone they personally dont like to benefit.

Which is their right as long as they are not discriminating against a protected class, as it's their work, but they should have put that in the license.

Forgive me for a naive question but how do external contributions to the AGPL code find their way back to the commercially licenced code?

Are all contributions to the "original" pre-licenced source? If so is there some extra legalese to ensure that the changes will always end up in the AGPL source too?

I know of many successful projects using dual licencing so it must work, I'm just wondering how on a legal front.

I don't understand all of your questions, but the proprietary part of the "dual license" can be anything the copyright holder wants. Qt is probably the most famous dual-license software. Check https://www.qt.io/pricing for some but not all details.

It looks like this is subscription-based, so I'm guessing you can update for the length of your subscription.

Perhaps you're asking whether you're allowed to use development patches written by external people that you'd maybe find in github discussions etc.? If you need that, you will probably have to negotiate for that option yourself. If that is your question, then that isn't really a naive question at all.

Outbound licenses (say, the GPL or proprietary) and inbound license for contributions are orthogonal. If you intend to dual license outbound, you need to clarify that in your inbound CLA.

The contributor would need to either:

- Agree to a Contributor License Agreement that grants the project owner an irrevocable world-wide commercial license (probably missing a few adjectives but you get the idea)

- Transfer the copyright

- Release to public domain

You publish under AGPL for free and also under a commercial license for people who do not want to abide to the conditions of the AGPL. See servicestack.net as an example. It seems to work for some people.

I think Atlassian have a dual licensing model where you can download the source code and build the product yourself, but only for single users, or open source projects.

Commercial users however have to buy a copy, but the source is available for all.

Maybe somebody could create a github (sharehub?) equivalent where anybody doing a clone has to register and then commercial entities can pay for the licence or single use hobbyists could attest.

people sharing the code can then set what they see as a fair price and the website will take a cut of the revenue (e.g. 30% ducks )