The total absence of CopyRight protection.

When something is "in the public domain", then anyone can take it, use it, copy it in any way they want. The author has given up all their exclusive rights - either voluntarily, or because the maximum term allowed by law has lapsed (normally lasts up to 70 or 90 years after the author's death, depending on which country you are in).

FreeSoftware is not in the public domain; it is covered by copyright and CopyLeft. Shareware used to inappropriately get called 'public domain software'; it's not. Just because something is free

If you want to put your software in the public domain, have a look at the Creative Commons Public Domain license. See See SoftwareLicensing.

Also the name of a rap group that NeilHawthorne? inevitably likes.

CategoryLicense