Login is not required for normal use of OrcaSlicer. The slicer can be used completely offline, and slicing itself does not require an account.
The login is primarily relevant for optional online functions, such as profile synchronization and backups. For certain printers, like Bambu models, registration with the respective manufacturer or alternatively, LAN mode may also be required.
An overview of setup, network connection and optional cloud features can be found here:
https://orcaslicer.org/guide/
This is an independent guide, not the official OrcaSlicer project page.