"Not jealous" is the next quality of love; and it is the first of several qualities that are attitudes toward other people that characterize love. Normally, we think of jealousy as being fearful or resentful towards someone because we are losing someone -- possibly, position or affection.
In the Bible, the word translated jealous can mean zeal or an ardent desire for or against someone. It can be good or bad. Since, the Bible says it is not jealous, it is intended to be the bad desire.
One occasionally hears someone say "I wish so-and-so were dead" or even, "I wish I was dead." It is pretty obvious from the Bible, that if a person says something, they mean it from their heart. It is possible that they may only mean it during the time they say it. But the Bible also recognizes that if something exists in a person's heart, it is as real as someone who has physically acted out that desire. The inner life is just as real to God as outer actions.
So, I am wondering if the real thrust of this quality is our attitudes toward people. Jealousy is not just resentment toward someone who is getting what I want. (Although, in the sense I am trying to describe, it certainly can be.) "Jealousy" is any attitude that is against another person. Wishing someone dies, fails or suffers some other type of misfortune is not having an attitude of love in your heart. Conversely, love is holding a positive desire in your heart for someone. Wishing health, success or good fortune for someone.
The Bible says that what we hold in our heart tends to show in our actions. So, if we hold a desire for good for someone in our heart, we tend to act for good for that someone.