Editing in the tree is disabled by default. So if your tree is editable, then you must be turning that on in code via the LabelEdit property, or other properties depending on the style of your tree.

So that leaves selecting, activating, and expanding/collapsing of nodes.There's no single property for all of these, but it's pretty simple to disable these.You could do something like this:

        private void Form1_Load(object sender, EventArgs e)
        {
            for (int i = 0; i < 10; i++)
            {
                UltraTreeNode parentNode = this.ultraTree1.Nodes.Add(null, "Parent" + i.ToString());
                for (int j = 0; j < 10; j++)
                {
                    parentNode.Nodes.Add(null, "Child " + j.ToString());
                }
            }
            this.ultraTree1.ExpandAll();

            this.ultraTree1.Override.SelectionType = SelectType.None;                
        }

        private void ultraTree1_BeforeActivate(object sender, CancelableNodeEventArgs e)
        {
            e.Cancel = true;
        }

        private void ultraTree1_BeforeCollapse(object sender, CancelableNodeEventArgs e)
        {
            e.Cancel = true;
        }

Another option would be to disable each node. You could do this when you add the node, or loop through the nodes recursively after they are added. Or, if your tree is bound, you could use the InitializeDataNode event to disable each node.