which are built on BSD licensed SPICE at Berkeley: "SPICE (Simulation Program with Integrated Circuit Emphasis) is a general-purpose, open-source analog electro

which are built on BSD licensed SPICE at Berkeley: "SPICE (Simulation Program with Integrated Circuit Emphasis) is a general-purpose, open-source analog electronic circuit simulator." https://en.wikipedia.org/wiki/SPICE https://en.wikipedia.org/wiki/SPICE Also see HSPICE, pSPICE, LTspice...