GPL License question

[yanshay]

I developed, as a hobby project, a device that communicates with a 3D printer (obviously not manufactured by me) and simplifies life with 3D printing for the end user. I showed it off in forums and the 3D printing community asked if I can make it available as Open Source.
I thought of offering it under GPL or AGPL which falls under your definition of Open Source.
I don't know however if this is considered an embedded system and what does it mean if it does if I want to release it as OpenSource in that case.
On your page - "Get Slint" when selecting GPLv3 and "Deploy on Embedded systems" there is 109USD monthly payment. I don't know if that's in case I deploy the software on the devices myself (which I don't plan to) or required also if this system is deployed by the end users themselves who purchase the relevant board and deploy it themselves.

Obviously the only option for me to release something like this is if I don't need to pay for any licenses, it's just a contribution to the community to have some fun.

• Happy to get some official clarification.
• Also, if it's ok to release it the way I thought of, any additional requirements I should be aware of?

[ogoffart]

If you choose the GPL (or the royalty free) license, you don't need to fill that form.
If you release your code as GPL or AGPL, you use Slint under that license and you don't need to pay anything.

[yanshay]

Thanks for the quick response.

1. I read some more your faq - am I correct to understand that if I choose the your GPLv3 path I can release my code under other licenses as well and not only GPL (e.g. MIT/BSD/Apache) (https://www.gnu.org/licenses/license-list.en.html#GPLCompatibleLicenses)?
2. From your answer - can I also use the royalty free in this case? so theoretically not even open source if wanted to, just give users the binary form free to install, with this application? I saw that royalty free excludes embedded system, but the definitions are not very clear to me. It's not really part of a system but rather integrate with a 3rd party system but it's also not a desktop nor mobile. So does it fall under embedded system or not for the purpose of Slint licensing?
3. And with either option, can I release my code under dual licensing, one for free usage and another commercial one to prevent someone from selling my software/embedding it and reselling it without my approval?

Sorry for so many non-technical questions, these licensing issues are more complex than developing applications 😄

[ogoffart]

1. Yes (If you chose a more liberal license, for example MIT, then the person that wants to redistribute your code can either continue to do so in an open source license, or using the royalty-free license on desktop, or pay a Slint license if they want to release your code as closed source)
2. It depends on where do the UI run. If the UI run on the user's desktop then this is a desktop app.
   If the UI runs on the screen of a 3D printer, then it is an embedded apps. Although we meant it more for the case where you distribute both the hardware and the software. Which is not your case. So perhaps the roylaty free license could work.
3. Yes, you can use dual license. If you use Slint under the GPL, at least one of the license need to be GPL-compatible, which cannot prevent commercial use. (But can prevent re-licensing under a proprietary license)

I hope this clarifies.

[yanshay]

2. It is neither. The Splint UI runs on the esp32 device itself (it is WT32-SC01-Plus which has a display connected to a PN532 NFC reader), sort of a very limited cheap standalone mobile phone in a 3d printed case. And indeed no plan to distribute any hardware. Users are makers and buy that separately if they want to use the software and flash it on their own. So would that be considered embedded under your terms to use under royalty free?

3. I saw a project in my space that seem to state that it is under GPL for non commercial use and for commercial use it's another license they present. If I understand that correctly though when using Slint under GPL I'm not allowed to do that because my code links with GPL? And that other project probably doesn't link with any GPL so can do that distinction of licenses?

So the question is if I can use Slint under royalty free path (which won't force me to the GPL constraints) and release my code as dual license - open source license for personal use and forbid commercial use?