BetterDiscordLibrary is temporarily down.

(BetterDiscordLibrary is NOT BetterDiscord)

Why?

For the past week or 2 the usage has been too high for the server. Resulting in database connection issues and today high resource usage.

I'm currently working on a quick replacement that will hopefully fix these issues. But of course will take some time.
A week or two I would think.

You can still get themes and plugins.

Either join the BetterDiscord Discord servers: Primary Server | Secondary Server
look inside the #official theme list / #official plugin list channels.

Or download the Theme Repo and Plugin Repo plugins by DevilBro.