I noticed the other night that our Mumble server is still working. However, there are a couple changes to be aware of. First, the download address is now simply
https://mumble.com, and the latest version is 1.3.2. It is pretty obvious there on the front page, so you'll have no problem finding it.
To set it up after you install it and get connected as directed above in the OP, make sure your mic and if using a headset, are hooked up. Go into your computer's sound settings, find your microphone, and ensure the boost checkbox is checked or the slider is turned up. Next, go back into Mumble and click on "Configure">"Settings" and click on "Audio Input" on the left if it's not highlighted already. Click the dropdown arrow beside of "Default Device" in the Interface box, and select your microphone device.
Now you need to set up a push to talk key. Mumble will do Voice Activation, but if you don't get it just right, it doesn't work well, and it's annoying. Please set up PTT. In the Transmission box, click the dropdown and select "Push to Talk." To set up a key, click on "Shortcuts" to the left. Click "Add" and then click on "Unassigned." Next, click the dropdown beside of "Unassigned", and select "Push to Talk." Now click to the right of "Push to Talk" right under "Shortcut." Find a key that you don't use much in your sim (so that you don't transmit while using that key in your sim.) Now just press that key, and Mumble will assign that key automatically.
Finally, click on "Audio Output" and in the same way that you chose your device for your microphone, choose your output device (usually headphones).
That's it. You can play with the volume on the Output page, but the other settings should work for you the way they are. There is a built text capability, so if things go wonky, I should be able to help you that way. Consider this your official invite to join us and chat.