The following is extracted from "One Life Five Precepts" by Venerable Faxun:
Conditions Under Which A Violation Is Considered to Have Occurred
- Object: A human being other than oneself
- Intention: The intent to misrepresent the truth and to deceive
- The Act: The act of communicating the untruth through words or gestures or by being silent
- Consequence: The person comprehends the meaning of the lie. Otherwise, our words are considered idle talk
- Unintentional misrepresentation
The use of speech to deceive is obvious, but the body too can be used as an instrument of communication – such as in writing (email, SMS, etc), hand signals, and gestures – all can be used to deceive others. The key element in this transgression is the intention. Therefore, there is no offense if a person misrepresents the truth unintentionally. For example, speaking too quickly and saying one thing while meaning to say another, such as a slip of the tongue.
The Intensity / Severity of Violation
The intensity of violation depends on the content of the untruth and the consequence of the untruthfulness. For example, it is a serious offense when a person, out of greed, lies that he/she has attained arahanthood, and the other person believes him/her.
The aim of observing this precept is to respect truthfulness. Speech is a way of expressing our thoughts. By being mindful with what we say and how we say it, we train ourselves to be more skillful speakers.
By giving up false speech, one becomes a speaker of truth. He does not deceive others, thus becoming a trustworthy and reliable person. Giving up slander, he reconciles those who are divided and brings them closer together. He strengthens friendships by living with love and harmony. Giving up harsh speech, he says what is gentle and pleasant, pleasing to the ear, affectionate and liked by most. Giving up idle chatter, he speaks at the right time in accordance with facts appropriate to the purpose, in accordance with the Dhamma. He speaks words worth treasuring, reasonable, appropriate, discriminating and to the point. (DN 1)
Furthermore, abandoning lying, the disciple of the noble ones abstains from lying. In doing so, he gives freedom from danger, freedom from animosity, freedom from oppression to limitless numbers of beings. In giving freedom from danger, freedom from animosity, freedom from oppression to limitless numbers of beings, he gains a share in limitless freedom from danger, freedom from animosity, and freedom from oppression. This is the fourth gift... (AN8.39)
Let's look at the specific examples that you gave. I know that John was kicked out of university because of bad conduct but when asked by a friend, I say, "John probably already moved to another university". All four criteria listed above are fulfilled, so this is considered a lie. According to the commentary, since all the criteria are fulfilled, the "kamma is completed", which means that the intention can potentially cause rebirth in an unwholesome plane of existence.
The Buddha also faced difficult situations when asked questions. In some cases, such as SN 42.2 and SN 42.3, the Buddha said, "Don't ask that question" in other cases, he refused to answer. In AN 5.198, the Buddha gave the criteria for Right Speech as "It is spoken at the right time. It is spoken in truth. It is spoken affectionately. It is spoken beneficially. It is spoken with a mind of good-will."
You asked "Is being honest the same as having wisdom?" Being honest is one aspect of Right Speech. Wisdom (paññā) involves turning the mind inwards through activities such as meditation, studying the Dhamma, teaching the Dhamma and straightening of views. So honesty can arise with or without wisdom. When honesty arises with wisdom there is awareness of the honesty.