Transparent Discord v1.0
Transparent Discord is far from perfect, but it's presently in a mostly-usable-if-incomplete state. The current feature set includes sending and receiving messages in guild, group, and private chats, creating private chats, receiving images, and setting an online status. Transparent Discord DOES NOT yet support joining guilds, adding friends, voice calls, message reactions, emoji, sending images and files, creating groups, and a number of other Discord features. The UI also still needs a lot of work, but should at least display all of the features I've mentioned it supports. I set out to create a Discord-based replacement for Google Hangouts's Transparent UI and I feel confident that I can achieve that goal. With basic functionality out of the way, my next goal is to bring this client up to par with Google Hangouts (creation of group chats, sending images, UI improvements, notifications, etc.). Following that, I will begin to implement Discord specific features (message reactions, custom emoji, etc.). From this point forward I will be including prebuilt jars with each commit, so if you want to try out the absolute newest version, feel free to check that out. These will probably be ugly and in a half-working state. If you want a more stable version, you can download the v1.0 release here. I'll do another release when I have enough new and stable features to warrant it or when bugfixes occur. If you run into any issues, please submit them to GitHub so that I can fix them. And finally, a big thanks to the creators of JDA. They've done an excellent job wrapping the Discord API, which has made this whole project a breeze on the backend.
How to retrieve your user token
To obtain your user token, go to the Discord web client. If using Chrome, open the inspector (Ctrl + Shift + I), go to the Application tab, under Local Storage in the sidebar, select https://discordapp.com, scroll to the bottom, and get the "token" value. Run the jar, and paste the token into the window. If you check remember, your token will be saved in a text file in the same directory as the jar. Be advised that the token is currently stored in plain text.
Disclaimer
I am in no way affiliated with the creators of JDA nor with Discord. The only data transmitted by this program is done via JDA. I do not collect any information using Transparent Discord. That being said, I take no responsibility for any harm that may come of running Transparent Discord, and you do so at your own risk. Keep in mind, if told to do so, Transparent Discord will store your Discord user token in plain text on your computer.