A method of software distribution where you let people copy your program, and trust them enough to say "if you like it, register your copy by sending me ''x'' amount of money." Pioneered by Jim Knopf (a.k.a Jim Button) with PC-File in 1981. It has the distinct advantage of near-zero distribution cost, but generally doesn't pay out quite like requiring people to pay up front for permission to even possess a copy of your software.

Modern ShareWare generally doesn't trust its users to pay up, so it resorts to disabling itself or nagging the user after a set period of time. This tends to frustrate the user, but apparently it works, much like dongle-based license managers frustrate the user yet apparently work. ("Works" is defined as making the user pay up.)

The Association of Shareware Professionals is alive and well at http://www.asp-shareware.org/.