gretl is described as 'Is a cross-platform software package for econometric analysis, written in the C programming language that can import SPSS data files'. There are more than 10 alternatives to gretl for a variety of platforms, including Windows, Mac, Linux, Xfce and Microsoft Office Excel. The best alternative is R (programming language), which is both free and Open Source. Other great apps like gretl are RStudio (Free, Open Source), PSPP (Free, Open Source), RKWard (Free, Open Source) and IBM SPSS Statistics (Paid).
MonteCarlito is a free Excel-add-in to do Monte-Carlo-simulations. Apart from these it can also do statistical analysis like mean, median, standard error, variance, skewness, kurtosis. It can create histograms. The code is open source.
Statwing was built by and for analysts, so you can clean data, explore relationships, and create charts in minutes instead of hours. Simply upload your spreadsheet or dataset, then select the relationships you want to explore.
WinBUGS is statistical software for Bayesian analysis using Markov chain Monte Carlo (MCMC) methods. It is based on the BUGS (Bayesian inference Using Gibbs Sampling). It runs under Microsoft Windows, though it can also be run on Linux using Wine.
Wizard is a new Mac app that makes data analysis easier than ever. No programming, no typing — just click and explore. Wizard includes a full set of tools for doing professional research, yet its friendly interface makes statistics accessible to beginners.