Qucs_cvs is a project mainly written in C++ and C, it's free.
Quite Universal Circuit Simulator
This git repository is UNOFFICIALLY copied from qucs.sourceforge.net, as described on their forum https://sourceforge.net/projects/qucs/forums/forum/311049/topic/3970384
Hopefully the qucs developers will take over changes made in this repository, otherwise I will at least try to stay in sinc with the CVS
fransschreuder