It's possible to install BirdieSync on a Standard user account (not Administrator) but there are presently a few restrictions during the installation.
First of all, the detection of the mobile device characteristics (operating system, processor) is not performed properly. You must manually choose the operating system of you mobile device.
Then each time you install a new version of BirdieSync under a Standard account, after the installation, it is mandatory to open BirdieSync options in Thunderbird or Sunbird and save them again to update the preferences format (this is not properly done by the installer because of the Standard account). Note also that even if you installed BirdieSync on another administrator account, it is necessary to do this procedure for the BirdieSync preferences under the Standard account.
If the mobile device had been previously connected to the computer under another user account, it's possible that the installer has problems stopping ActiveSync or the Windows Mobile Device Center because it doesn't have the right privileges. In which case, it is necessary to manually restart ActiveSync or restart the WMDC (with administrative privileges to stop the processes).
You may also have to stop Thunderbird or Sunbird if it was started on another user account.