Although the total angular momentum of the entire cluster is near zero, thus their spherical shapes, individual stars orbit the center of mass of the cluster along plunging or elliptical orbits. For any one star, the star is in a circular orbit around the center of the cluster which is stable for billions of years, though probably gets perturbed by close gravitational encounters in the inner core. A small dribble of stars get ejected at the outer edge of the cluster because innumerable 'slingshot' encounters over millions of years have added energy to the stars motion so that its orbit slowly develops an apastron 'farthest orbit point' just outside the tidal radius of the cluster. The star then escapes the cluster. This is the principle reason why, over billions of years, globular clusters slowly evaporate.