OpenOffice multiple launcher in launchpad/dock
Unfortunately, I believe this isn't possible, not because of a Mac issue, but because the OpenOffice team chose to have it work this way.    

I had found this site here which provided some app launch icons, though it seems it may be out of date and these may no longer work.   

The site does have a "workaround" posted...  which is the following:

Just an FYI. I have found that in OpenOffice 3.2 running on Windows there is an openoffice icon in the system tray that when right clicked allows you to open any individual application directly. On a Mac simply keeping the openoffice icon in the dock and then right clicking it gives you the same capability.

Given this... it seems OpenOffice decided that the "right way" to access a specific app from the dock is right-clicking and then picking the one you want.   

Not exactly what you are looking for...  but might be the closest you'll get.