Complex sentence: The prevalent use of captive portals is for user authentication, however captive portals are gaining increasing use on free open wireless networks where instead of authenticating users, they often display a message from the provider along with the terms of use.
Split into simpler sentences: The prevalent use of captive portals is for user authentication, however alternate and/or supplemental use cases exist. Captive portals are gaining increasing use on free open wireless networks where instead of authenticating users, they often display a message from the provider along with the terms of use.