Where in this article does it saying anything about any labor being "forced" or even compelled (such that any necessity of life is denied any who choose not to

Where in this article does it saying anything about any labor being "forced" or even compelled (such that any necessity of life is denied any who choose not to participate in these activities)? You are stretching a definition of "slavery" to encompass simple incarceration. That cheapens the word. Is there actually forced labor in present-day civilian prisons? (Courts-martial have traditionally been allowed to impose sentences "at labor", but I have not observed this in the civilian case).