(Disclaimer: Not a lawyer, but a number of my projects are licensed under MPL)
As I read it, the only time the MPL requires you to share source code is when you modify files belonging to the MPL-covered library. Even then, it only requires you to share the changes you made to the library - you don't have to share any of your proprietary or non-MPL code.
From TL;DRLegal: "You must make the source code for any of your changes available under MPL, but you can combine the MPL software with proprietary code, as long as you keep the MPL code in separate files."
So - did you install a MPL library using a package manager like npm or pip? You do not have to share your project's code.
Did you copy/paste a MPL library into a /vendor/mpl-library/ directory? You do not have to share your projects code.
Did you copy/paste functions from a MPL library directly into your source code? In this case, you may have to share the file you pasted into, but not any other files in your project.
Overall, I think the MPL strikes a great balance between the "do what you want" crowd and the "people should give back to projects that help them" crowd, which is why it's my go-to license for most libraries these days.
As I read it, the only time the MPL requires you to share source code is when you modify files belonging to the MPL-covered library. Even then, it only requires you to share the changes you made to the library - you don't have to share any of your proprietary or non-MPL code.
From TL;DRLegal: "You must make the source code for any of your changes available under MPL, but you can combine the MPL software with proprietary code, as long as you keep the MPL code in separate files."
So - did you install a MPL library using a package manager like npm or pip? You do not have to share your project's code.
Did you copy/paste a MPL library into a /vendor/mpl-library/ directory? You do not have to share your projects code.
Did you copy/paste functions from a MPL library directly into your source code? In this case, you may have to share the file you pasted into, but not any other files in your project.
Overall, I think the MPL strikes a great balance between the "do what you want" crowd and the "people should give back to projects that help them" crowd, which is why it's my go-to license for most libraries these days.