This usually means Gatekeeper is blocking an unverified developer. Go to System Preferences > Security & Privacy > General and click "Open Anyway".
However, the concept of "new" in software preservation is paradoxical. As Apple continues to update macOS, breaking compatibility with older 32-bit applications and changing underlying architecture (most notably the shift from Intel to Apple Silicon with the M1/M2/M3 chips), older versions of software like 10.4.5 become obsolete. Yet, they also become historical artifacts. final cut pro x 1045 macdmg new
Purchase the software or click if you already own an older version. This usually means Gatekeeper is blocking an unverified