With the Ajax client, a document can be open by a user only once with a Named CAL, else the last connection will kill the previous one.
For example, the user opens Document1.qvw in tab1 of the browser, clicks around, and minutes later opens Document1.qvw also in tab2, or in a different browser, and clicks around. The latter session will be kept, while the previous in tab1 will be killed. This is the expected behavior.
The user can indeed have QlikView Desktop, or Ajax, in as many computers as required, that is not a problem. The session created can exist only in one place for a given user and a given document. A user can open as many apps as he or she wants to.
It is worth noting that, using QlikView Desktop, it is indeed possible to open several times the same QVW, however, the last version of such QVW to be saved will overwrite the previous.
Finally, if a user does need to have the same document open twice because comparisons, you can always distribute the same application twice, either with different names or to different locations, but the data set and the layout will be exactly the same.
Hmmm, maybe the situation is even trickier. AFAIK (tested again on QV12.20SR6)
The same user cannot open two sessions on different platforms using a single CAL
The same user cannot open two sessions on the same platform using a single CAL in different applications (e.g. a browser and QV Desktop's Open in Server, or two different browsers)
You can however:
launch multiple sessions in a single browser and keep them alive (see below for what happens if two sessions visit the same document)
Launch multiple instances of the same application/browser on a single platform, open a session in each one of them and keep them alive.
In the latter cases, you won't get any messages about Killed Sessions or revoked Named CALS in the QVS Events log.
There is one adverse effect of opening the same document twice as specified in the last bullet list: each session inherits the last set of selections you make. For example, if you launch two instances of the same browser on your machine and open the same document in each one of them and make some selections in browser 1, then switch to browser 2 and select a different sheet (or make any other change that will force a redisplay), the selections made in browser 1 will appear in browser 2 as well. But the sessions will not be closed and reopened.
It looks like you are sharing a single session which will hamper your ability to do comparative analysis, ...