We are going to build a sample isomorphic application by using JavaScript cross-stack. Therefore, the only requirement is to have the latest version of Node.js installed on your machine plus a text editor or IDE with ES6/ES2015 and JSX support. If you don't have Node.js installed, you can find the concrete steps on how to install it on the https://nodejs.org website.
Note
WebStorm, Atom, or Sublime Text 3 are generally considered good option. Those can run on any platform. Just make sure that your text editor is properly configured to work with ES6/ES2015 JavaScript, JSX, and ESLint.
Optionally, you can also install the React Developer Tools extension for Google Chrome or Firefox to help you with debugging React apps in the browser.