My terms of service are that you are not allowed to breath oxygen.
I am getting a bit tired of companies being able to have user hostile, anticompetitive, monopolistic terms of service. The freedom we give them comes at the cost of the freedom as consumers to have free markets because they lock them up
Illicit means maybe against the law but definitely against the rules, for example an illicit affair. The word for against the law is illegal, from Latin, or unlawful, from Germanic. I guess the Germanic cousin of "illicit" would be "forbidden."
"Licit" in English usage also carries the weight of its connotation in church ("canon") law, wherein it can refer to acts that are considered not only to have occurred spiritually ("valid") according to the law, but have been done in conformity with the process laid out in the law.
For example, canon law asserts that certain sacraments such as marriage or baptism can be conducted validly but illicitly, such that the marriage is still considered to have occurred, but it wasn't done the "right way." In contrast, there are some things that, if done illicitly, aren't valid either. (In this case I think it's because there's a notion that there's a supernatural/spiritual aspect to certain acts that transcends whether they're done licitly, whereas certain other acts are purely creations of human law and therefore if not done licitly are void ab initio.)
Extramarital affairs are against the law in many countries and 17 US states. “Illicit affair” is potentially a holdover from when it was illegal more places, not just a conflating of against the rules with illegality.