installer .app wont run under OS X 10.3 (panther) ?

running OSX 10.3 (panther) G4 powerbook
downloaded
http://www.downloads.bt.com/btbroadb...taller.app.sit
and extracted installer .app with stuffit

Have emailed BT to ask if it runs under 10.3 but had no reply,
anyone else got this running ??
( or the BT supplied voyager 105 USB modem working with a Mac.
NB: this adsl modem was supplied to work (and does) with a PC, but now
need to access Internet with the Mac, and the drivers
are on their site for download so it should work, right? )

Any help much appreciated,
Thanks.