Add the user to daemon group.
There should be security risk adding user used as login acount.
On Terminal app type
sudo dseditgroup -o edit -a Usernametoadd -t user daemon
I didn't test it myself yet.
I did it on OSX10.9 and succeeded.
Tested only AdminConsole and access Server_Sample by WEBDirect.
If you have no special reason to use admin username, use default fmserver may be best.
After uninstalling trial version, the folder
still may be exist.
Delete or rename it before install another server.