Open science licenses
Formally licensing your research products with a recognized license (for example, through a Creative Commons license or an Open Data Commons license) provides a consistent and easily understandable way of communicating how other people can interact with those products. Guidelines like the Panton Principles for data sharing give recommendations for licenses that are appropriate for practicing open science.
A good guideline is to use a license that places the fewest restrictions on use of your work as possible (for example, CC-BY, a Creative Common license which allows folks to do whatever they want with your work, provided that they give proper credit, or CC0, a Creative Commons license which places your work in the public domain). For a primer to software licensing with a focus on R packages, check out Karl Broman’s discussion on software licenses for R packages.