Amateur and Non pros

Amateur noun - A person who regularly or occasionally engages in an activity as a pastime rather than as a profession.

Non pros and amateur are semantically related. In some cases you can replace phrase "Non pros" with "Amateur", this terms are similar.

Non pros noun - A judgment entered in favor of the defendant when the plaintiff has not continued his action (e.g., has not appeared in court).

Amateur and non pros are semantically related. You can use "Amateur" instead a noun phrase "Non pros".