I have made an arbor layout with cytoscape using
layout{
name:'arbor'
}
But as seen in arbor.js, the nodes are bouncing freely. It doesn't seem to happen in cytoscape layout. After loading in the browser, once it is rendered freely, after that it becomes an static one.
The behaviour you describe is not expected or desired by default for the vast majority of users of the library, so I doubt this default behaviour will change.
You'll have to configure your layout options appropriately for what you want. The options do what's documented, so you just have to change the options related to ending the layout:
http://cytoscape.github.io/cytoscape.js/#layouts/arbor