Yes, developers can enable their end-users to login using OAuth. You can read more about OAuth here.

What is OAuth Support? An Easy Way to Offer Commission-Free Trading Directly on Your App!
Add Alpaca’s commission-free trading capability inside of your app with the minimum effort through a commonly used integration method of OAuth.
OAuth Integration Guide - Documentation | Alpaca
Alpaca supports OAuth for anyone who builds apps and services using trading API. Alpaca API lets you build and trade with real-time market data for free.