> Our goal is a linkable library, which makes GPL impossible

Not impossible. It forces the code using the library to be under a GPL-compatible license and requires the binary to be released under the GPL license.

The distinction is quite important. It's only impossible in the mind of someone who wants to release proprietary software. Even for people releasing software under permissive license it's not impossible, just highly inconvenient (and the LGPL is always an option in this case).