Frax is described as 'art program that puts the “equations of nature” in the palm of your hand. Frax is powered by fractal geometry, the same principle that creates patterns of self-similarity in our natural world'. There are more than 10 alternatives to Frax for a variety of platforms, including Windows, Mac, Linux, Online / Web-based and Android. The best alternative is Xaos, which is both free and Open Source. Other great apps like Frax are Apophysis (Free, Open Source), Ultra Fractal (Paid), Chaoscope (Free) and ChaosPro (Free).
XaoS is an interactive fractal zoomer. It allows the user to continuously zoom in or out of a fractal in a fluid, continuous motion. This capability makes XaoS great for exploring fractals, and it’s fun!
Apophysis is a fractal flame editor and renderer for Microsoft Windows. It was created by Mark Townsend by translating Scott Draves original C code into Delphi and adding a graphical user interface.
Ultra Fractal is a fractal generation and rendering software application. The program works using a similar paradigm to Photoshop, allowing multiple layers to be combined using layer blending modes, transformations and custom fractal formulas.
Chaoscope is a 3D strange attractors rendering software. The word "Chaoscope" was invented by Ralph Abraham to describe computer tools used to help comprehending dynamic systems, a superset of the strange attractors.
XFractLab is a program to render fractals using specialized formulas. Built in compiler lets you image a wide variety of fractals while maintaining high performance. Multithreaded renderer scales with any number of cores, allowing to use your machine to its full capabilities.