Is Maronite a Catholic church?

Yes, the Maronite Rite is a part of the Catholic Church.
Yes it is, it all falls under the Catholic Church. They celebrate the same things as Roman Catholics, therefore Maronites are part of the Catholic Religion. I am Maronite.

Roman Catholic Answer

The Maronite Church is actually a "rite" within the Catholic Church. It is every bit as much a Catholic Church as the familiar Latin Rite is to those in the western world.

Roman Catholic Answer

The Maronite Rite is part of the Catholic Church.
If by "Church" you mean "religion", there is no such thing as a Maronite religion. The Maronites are in full communion with the Catholic Church, believe all that the Catholic Church teaches and are Catholics in the full sense of the word. The Maronites are merely a separate "rite", meaning that they have a different way of celebrating Mass than what is known by most Westerners, which is the Roman Rite or the Latin Rite.
Most people do not know that there are different "rites" i.e., methods, of celebrating the Holy Sacrifice of the Mass. Most Westerners are only accustomed to the Roman (a.k.a. Latin) Rite which is by far the most widespread of all the different rites.
Most of the other rites are found predominantly in Eastern Europe, Africa, and Asia, although those different rites can be found occasionally elsewhere too.
Some of the different rites I can think of off the top of my head are:

1) the Roman Rite 2) the Byzantine Rite 3) the Maronite Rite 4) the Mozarabic Rite 5) the Milanese Rite 6) the Coptic Rite

If a Catholic of the Roman (Latin) Rite were to attend Mass in one of these different rites they might not even realize they were at a True Mass or in a Catholic Church because most Catholics only have exposure to the Roman Rite. However, the Priests who perform those other rites are true Priests just as Priests of the Roman Rite and those other rites have the same true Sacrifice of the Mass and the Real Presence of Our Lord in the Blessed Sacrament just as the Roman Rite does.