At the moment when disabling a RadTreeNode on server/client side the complete node gets disabled with the CheckBox.
We had a use case where we would like the node to stay functional (collapsable/expandable/clickable/hover-effect) but only the checkbox to become disabled.
As this can't be achieved with the RadTreeView we had to build a work-around for that. Most likely people in need of this feature make a new HTML-variable to store/transmit/apply the state of the checkbox since the manipulation of the Checkboxes gets lost in a postback.
This would have to be implemented as a server/client-feature as it is with the enabled/disabled-state of the RadTreeNode.