I released spreadsheets under the MIT license two weeks ago. Spreadsheets is a package (extension) for Renjin (an implementation of R for the Java Virtual Machine). This package will give you the ability to work with (read, write) spreadsheets. It supports reading of excel and Open Office/Libre Office spreadsheets files. The project is located on github.
Xmlr is a R packed providing an object oriented approach to XML management for R written in R’s Reference Classes. The project is located at github and available for free under the MIT license. It was accepted by CRAN May 12 2020.