It is no problem to run Limesurvey in a shared database. However, Limesurvey will need more than one table.
When you are asked for the database, you just give it the details of the existing database. What is important here is that the prefix that you can give the limesurvey tables is different from the one of the other aplication using the same database.
But with the prefix "lime_" or "limesurvey_" you should be fine, as long as you don't want to run to LS-Installations in the same database.