CloudStat is described as 'is the cloud environment for building statistical applications collaboratively'. There are more than 25 alternatives to CloudStat, not only websites but also apps for a variety of platforms, including Windows, Linux, Mac and Android. The best alternative is GNU Octave, which is both free and Open Source. Other great sites and apps similar to CloudStat are R (programming language) (Free, Open Source), MATLAB (Paid), RStudio (Free, Open Source) and Mathematica (Paid).
Octave is a computer program for performing numerical computations which is mostly compatible with MATLAB. It is part of the GNU Project. It is free software under the terms of the GNU General Public License.
MATLAB is a numerical computing environment and programming language. Maintained by The MathWorks, MATLAB allows easy matrix manipulation, plotting of functions and data, implementation of algorithms, creation of user interfaces, and interfacing with programs in other languages.
SageMath is a free open-source mathematics software system licensed under the GPL. It builds on top of many existing open-source packages: NumPy, SciPy, matplotlib, Sympy, Maxima, GAP, FLINT, R and many more.
Spyder (previously known as Pydee) is a free open-source Python development environment providing MATLAB-like features in a simple and light-weighted software, available for Windows XP/Vista/7, GNU/Linux and Mac OS X.
Orange is an open-source, cross-platform data mining and machine learning suite. It features visual programming as intuitive means of combining data analysis and interactive visualization methods into powerful workflows.