Broadcast is usually off by default for MMORPG games, unless you selected to have it turned on by default in the Quick Setup Wizard (although D3/D2R and other similar generic broadcasting style games may set this by default).
If you need to change this, you can remove the setting here by clicking on the < button and setting the Key Map and Mapped Key drop downs to the EMPTY option at the top of the drop down.
If you want Key Maps to be off by default, this has a couple of different methods depending on the desired outcome.
The "easy" method is to change the above mapped key to be the "Activate Maps (all windows)" mapped key in the Mapped Key drop down (ignore the warning).
The more complete option, is to go to your character set keymaps, and unhighlight all the Key Maps with the word HOTKEYS in the name
And then, go to Key Maps -> ISB42 - Toggles, Activate Maps (all windows), expand out the Steps, select Step 2 on the left, and press ALT+UP, so it moves step 2 to step 1. You will also need to edit the last Action in each step so they point to the Other step (i.e. the action in Step 1 should point to Step 2 and the action in Step 2 should point to step 1).
The new Step 1 turns things On.