Regarding sharing objects it seems it's possible (I just tried) with IE plugin to share objects with everyone or share by username (domain\user); in Server Objects Pane, R click on a Shared Object and choose Share Permissions
The response from Mario is correct, however I do not believe you can then restrict who can see the newly created object and who can't. You can definitely control who has permissions to create additional objects, but I am not sure you can then control who sees these new objects themselves.
you can follow Mario's post: in Qlikview server goto System --> Setup, choose your server and in Documents tab flag "Allow Server Objects". You can find more in online help on your server (I copied it, see below)
I just tried in a browser with AJAX (so it should work for IE plugin and AJAX too)
add an object to a document -->R click on it --> Options --> More --> Share ..... (see image)
To allow users to share sessions on documents, tick this check box. To deny users to share sessions on documents, untick this check box.
Allow Server Objects
Note! When collaboration is disabled in the QlikView license (that is, the license containsDISABLE_COLLABORATION;YES;;), server objects and server bookmarks are not allowed. This means that the Allow Server Objects and Allow Anonymous Server Bookmarks check boxes cannot be checked when collaboration is disabled.
To allow the users to create server objects, that is, Sheet Objects and Reports, tick this check box. To deny the creation of server objects, untick this check box.
Note! When the check box is unticked, no server objects, except server bookmarks, can be created. For server bookmarks, unticking the check box only affects the possibility to share the bookmarks with other users.
Allow Anonymous Server Bookmarks Anonymous users can be allowed to create bookmarks. The machine ID of the user client is used for ownership, and the user client has to allow persistent cookies to be created. To allow anonymous users to create bookmarks, tick this check box. To deny anonymous users to create bookmarks, untick this check box.