DISTRHO is an open-source project for Cross-Platform Audio Plugins.
We provide our own plugins and Linux ports, everything being open-source. LV2 and VST versions are always available, sometimes with LADSPA and DSSI as well. Our main target platform is Linux, but we support Windows and Mac too.
Our entire source code is available in GitHub: https://github.com/DISTRHO. Third parties are welcome to share their code with us if they want to see a Linux port. Contact the project leader, falkTX, if you're interested on this.