Download of R 4.0.3 for Mac was on the developer's website when we last checked. We cannot confirm if there is a free download of this app available. The most popular versions of R for Mac are 3.0 and 2.1. The application lies within Education Tools, more precisely Science.
This free Mac application was originally produced by org.R-project. The latest version of R can be installed on Mac OS X MIN_VERSION or later. Please check the Mac app with an antivirus before launch as it is downloaded from the developer's website, and we cannot ensure that it is safe. The unique identifier for this application's bundle is org.R-project.R. Commonly, this program's installer has the following filename: r-3.0.0.pkg.
From the developer:
R is a language and environment for statistical computing and graphics. It is a GNU project which is similar to the S language and environment which was developed at Bell Laboratories (formerly AT&T, now Lucent Technologies) by John Chambers and colleagues. R can be considered as a different implementation of S. There are some important differences, but much code written for S runs unaltered under R.
You may want to check out more Mac applications, such as Stellarium, Mathematica or LaTeXiT, which might be similar to R.