> So, It's best to use permissible license for the open-source version of the application in case of dual-license if we want to take back the contributions to our non open-source version.
That's one option; the other is to require that contributors assign you copyright of their contributions (perhaps with compensation) so you can release it in the same manner as your own code.
Narrowly focused on the effectiveness of the dual license scheme itself, permissive licenses "don't work as well" because there is less incentive for anyone to pay you for the other license; typically all they'd be avoiding is the attribution requirements.
> That's one option; the other is to require that contributors assign you copyright of their contributions (perhaps with compensation)
I thought about it before I made my previous comment, Good to know this is a thing.
> permissive licenses "don't work as well" because there is less incentive for anyone to pay you for the other license; typically all they'd be avoiding is the attribution requirements.
As far consumers are concerned, I think it largely depends upon the project; If it's complex to setup and run then I guess people would use the hosted version. I use open-source Aseprite because it's available on AUR, But I did pay for the license on their website which I presume most wouldn't.
Perhaps the real concern with permissible license are the competitors, Who get to use your code to reduce their barrier for entry. Then again, Software code at current times aren't that big of a barrier to entry.
One thing which all these discussions prove to me is that open-source application funding is very complex, Depending upon it for livelihood with just good will of the consumers is very risky as consumers are on average poor and corporations are on average greedy.
As you say, it depends a lot on the project, but you're thinking too narrowly when it comes to types of projects. IME, dual license is most applicable to libraries that might wind up in native applications. With, say, "GPL or pay us for proprietary" a company trying to ship a native app is faced with the choice of not using the library, paying for the library, or releasing their product under the GPL to use the library while avoiding paying for it.
Interesting find, I took a cursory look at their GitHub[1] and they seem to accept PR from outside but I didn't find any explicit mention of copyright transfer; Perhaps because there's no separate version of sequence.js for commercial use(Just use case differentiation).
> there's no separate version of sequence.js for commercial use
A separate version is "open core", not "dual license" - that's a different business model.
Use case differentiation by means of providing the same thing under different licenses is what dual license (or multi license) means. One license (say, GPL) will be appropriate to some use cases (downstream open source projects) but not for other use cases (downstream proprietary software) and so the latter has to pay for a license other than the GPL.
> I didn't find any explicit mention of copyright transfer
It's possible they know the people who've submitted code outside of github and handled it out of band, or that github has some way I've missed of requiring submissions to assign copyright in a way that wouldn't be visible to us. It's also possible they're being legally reckless and might be subjecting their paying customers to potential (if perhaps unlikely) copyright claims from their submitters. There is nothing about it being the same code under both licenses that would imply they wouldn't need their submitters' blessing in some form to sell their code under the proprietary license, and the more implicit blessing the more likely it'll wind up in court at some point.
> the need for having a permissible license for the dual-license.
A more permissive license generally improves adoption. For the same level of adoption, a less permissive license drives more revenue in the dual-license model. Maybe a permissive license is still the way to go (certainly getting adoption is often difficult), but it is not the dual license situation motivating that. Contrast a "give away the software and sell support" business model, where (sufficient) adoption is everything and more restrictions on the license doesn't do anything for the business.
With a maximally permissive license, I hesitate to call it "dual licensing", as it stops being the license your paying customers are actually paying for but rather hosting, support, or warm fuzzies.
> a less permissive license drives more revenue in the dual-license model.
But we've so far encountered just one example for that, Even there we don't know the financial status to claim whether it's indeed more successful (revenue wise when compared to a permissible license).
On the other hand we have numerous successful products (by revenue) with permissible licenses incl. those sighted in the OP.
That's one option; the other is to require that contributors assign you copyright of their contributions (perhaps with compensation) so you can release it in the same manner as your own code.
Narrowly focused on the effectiveness of the dual license scheme itself, permissive licenses "don't work as well" because there is less incentive for anyone to pay you for the other license; typically all they'd be avoiding is the attribution requirements.