This is exactly the Ardour model (and what Aseprite did before their license change). It's a highly viable way to sustain a niche FOSS desktop app in 2026. Make the repo open source, but put a price tag on the official, signed binaries on the main website. The professionals who need this to get work done will gladly pay a fee to avoid spending an afternoon fighting with Avalonia dependencies and build environments. The starving students and FOSS purists can clone the repo and run the build scripts themselves.

Isn't it dangerous to give up all the code of a commercial software in the age of LLM?

Competition can clone the project in another language and lipstick it to look different.