>(1) If you statically link against an LGPLed library, you must also provide your application in an object (not necessarily source) format, so that a user has the opportunity to modify the library and relink the application.
This is covered in sections 6 and 6a of the LGPL 2.1.
Hello, I am the author of VkFFT. When I made VkFFT I wanted license to be like this: your project doesn't have to be open-source, but please share your modifications to VkFFT. I think about switching it to MPL 2.0, is this one better for everybody?
Goal of LGPL is to protect freedom of developers to modify code of a library (e.g. to improve it, fix bugs, fix incompatibilities, port to new hardware, etc.) shipped as part of proprietary application. This freedom is important for developers of niche OS'es. This protection works, because of hard consequences for proprietary code in case of license violation: proprietary code must be released under GPL then.
MPL doesn't protect such developers, but it "forces" contribution of changes back to original code. In reality, it's ignored.
Header-only library cannot be compiled as separate library, so requirements of LGPL cannot be met by proprietary code.
That would probably do what you want because it applies on a per-file basis and not to the entire program, but make sure you read the MPL FAQ and the fine print before making such a change: https://www.mozilla.org/en-US/MPL/2.0/FAQ/
So then the OP is a LGPL header-only library, which is always statically compiled in every source. Do we need to do the same thing, and if yes, how we provide an application to allow recompiling?
If you can't use the object files to rebuild another version of the program with a modifier version of the library then no that probably wouldn't be compliant. In that case you would probably have to modify the library so it's not inlining every function. (Disclaimer: IANAL)
https://www.gnu.org/licenses/gpl-faq.en.html#LGPLStaticVsDyn...
>(1) If you statically link against an LGPLed library, you must also provide your application in an object (not necessarily source) format, so that a user has the opportunity to modify the library and relink the application.
This is covered in sections 6 and 6a of the LGPL 2.1.