Multitaneous applications are those that allow many people to be editing the same work product (e.g. document) at the same time.
In the conventional workspace approach, the person editing the work product must lock it. This causes a vicious circle whereby people have to wait to get the lock, and then for fear of not getting it again hold on to the lock for as long as possible. This means other people have to wait and they hold onto the lock for as long as possible and the problem escalates.
In multitaneous applications only the fine grained object being edited (e.g. a block of text) is locked, and it is locked automatically and only locked until 2 seconds after no fresh changes have been made. This means that work products become like busy streets that many people at once can be walking on, only taking up the space they are walking on, and that space becomes free as soon as they move on. This compares with the workspace approach which is analagous to someone locking an entire street in order to walk on it.
An example Multitaneous application is the SharedPage MultitaneousEditor which can be launched with the Webstart Link http://www.sharedpage.com/download/Multitaneous.jnlp