Your TL;DR should read "...source code and a virtual environment that allows the process to be repeated..."

From the article:

"There has been significant pressure for scientists to make their code open, but this is not enough. Even if I hired the only postdoc who can get the code to work, she might have forgotten the exact details of how an experiment was run."

also

"The only way to ensure recomputability is to provide virtual machines"

To that end, the site http://recomputation.org/ is mentioned as a repository for recomputable experiments.

Point being: source code alone does not specify the process or workflow in which it was used.