You need to place the right library file under READYAPI_HOME/bin/ext directory and remove the rest of the files from both the places.
READYAPI_HOME/lib directory is for the libraries provided by SmartBear with ready api.
It is best practise to place the user libraries under READYAPI_HOME/bin/ext directory, so that it is very is easy to identify what extra libraries you are using and avoid confusion later for you and also easy to replicate the same environment for your colleagues.
Regarding multiple versions, jvm loads the file which ever comes first and no order in particular. Better to have only the needed / right file and avoid multiple versions of the same library.
