F* is described as 'ML-like functional programming language aimed at program verification. F can express precise specifications for programs, including functional correctness properties. Programs written in F* can be translated to OCaml or F# for execution'* and is a programming language in the development category. There are five alternatives to F* for Mac, Windows, Linux and BSD. The best alternative is F# (programming language), which is both free and Open Source. Other great apps like F* are Isabelle, Coq, Agda and OCaml.
Coq is a proof assistant, which allows you to write mathematical proofs in a rigorous and formal way, and have them checked for correctness by the computer. It also allows programming with proofs of correctness for the code, and dependent types.