Discord is a completely free to use voice-chat with no gotchas. This means you can make as many servers as you want with no slot limitations. For more information on the features Discord offers, visit them at discordapp.com
Technic offers Discord integration in our major modpacks with a custom mod McDiscord, but you can also include this mod straight in your own modpack. This will show your users how many clients are connected to your Discord server and they can also click on a link to quickly join voice chat straight from the game. It's never been easier to get voice chat on your server!
If you enter your Discord server ID on the Platform, we will add the Discord server embed straight on your modpacks page. Also, the launcher will display a "Join Voice Chat" button on your modpack as well as an active user count.
Discord integration will continue to grow as well. We plan in the near future to allow the mod to communicate all text chat between Discord and your Minecraft server allowing everyone to stay in touch no matter where they are!
Once you create your own free Discord server you can access your server ID by going to Server Settings->Widget and clicking the copy button next to Server ID. Make sure to click "Enable Widget" or the integration will not function properly.