This idea has been merged into another idea. To comment or vote on this idea, please visit CF-I-2721 Make the Curse launcher launchable offline so that games can be played where there is no internet available.
I'm not sure if this is a bug but yesterday my internet went out and I figured that I'd just play some single player modded minecraft while I waited for it to come back. Instead I was greeted with an error and locked out of the curseforge launcher. It really doesn't make sense to not be able to play the mods while offline.