5spice is described as 'Spice based electronic circuit simulation and circuit analysis software. 5Spice has the analysis capabilities needed by experienced circuit designers while remaining easy to use' and is an app in the Education & Reference category. There are four alternatives to 5spice for Linux, Online / Web-based, Windows and Mac. The best alternative is gEDA Project, which is both free and Open Source. Other great apps like 5spice are CircuitLab (Paid), Circuit Tree (Free Personal) and ModelSim (Freemium).
The gEDA project has produced and continues working on a full GPL'd suite and toolkit of Electronic Design Automation tools. These tools are used for electrical circuit design, schematic capture, simulation, prototyping, and production.
Sketch, simulate, and share your circuits, entirely in your browser -- no install required. Easy schematic capture and powerful SPICE-like, mixed-mode circuit simulation helps EE students, electronics hobbyists, and electrical engineers design faster.