Which license should I use if I want my code to not be used to make a paid service ?

I does not know about licenses which directly prevent commercial usage.

You could look up Gnu GPL (https://tldrlegal.com/license/...-(gpl-3)#fulltext) which make the seller to give up the source code (in my knowledge).

I think most company does not want to give up their source code which in turn prevent commercial usage.

or actually just stamp it with a CC BY-NC-SA 2.0 licence, it allows people to use/modify but not for commercial use

https://creativecommons.org/license...

@mr-user Not correct - if anything, that should be the AGPL.

The point is that with the GPL, the seller only needs to give the source to those whom he gave the binary. In case of a (backend) service, the binary runs only on his server, so he doesn't have to give the source code to anyone.

Also, neither GPL nor AGPL forbid selling the product, which of course cannot be the source code itself because everyone can fork it for less and ruin the business. But build some service on top of that, like Facebook with the people networking effect, and that creates enough value.

For example, some of my GPL code is actually being used in commercial products.

If you want to remain FLOSS ("free/libre open source") there is none, as any FLOSS licence must grand the user an unlimited and and restricted _usage_ right. On the other hand there are licences that can make companies not want using your software (but they legally could, and sometimes still do):

- GPL: If they include your software, they would have release any modification to it and if directly integrated into their apps source code the whole code of their app.

- AGPL: There is a loophole in the GPL, if a company does not have binary releases, but SaaS. The AGPL forces to even publish modifications to any service use. The AGPL is banned at many companies.

Still, this does not prevent making a product with your software: MongoDB tried to invent a new licence to prevent it, but with a major backslash in the community, and strictly speaking it is not free software any more.

Any CC-*-NC can be used as well, but are unlikely to be seen as "FLOSS" by definition.

(Continuation)
If you did not mean FLOSS but open source in a literal way (as "source available"): The MongoDB, CC-*-NC or even your own, custom licence can be used.

Just remember, that it might be difficult to get the definition of "paid service" and to put your idea in words:
- SaaS?
- A software store (its a service and it is paid!)
- A nonprofit company (it still has to be paid, but makes no profit)
- A system administrator contractor who wishes to install it for a school (put take money for the amount of work)

What I am trying to do is a kind of SaaS. It's quite simple but when I searched the same thing on Google, I found many paid services (I searched a simple feature request board) which is totally ridiculous, so I just don't want a company to use my work to make a new paid service.

Check out the this one for inspiration https://zeebe.io/faq/...