While activity badges may only be used for one program, you are able to duplicate existing activity badges (formerly learning tracks) within program/challenge setup.
Get there: Setup > Manage Programs/Challenges. Either select and edit an existing program or create a new program.
Set up and/or confirm the first page of "program setup" items, and then move to the "Badges" section of your program:
At the bottom of the page you will find a button to "Duplicate" an existing badge.
From here you can select the activity badge you wish to duplicate.
When an activity badge is selected the other activity badges will disappear. You can only duplicate one activity badge at a time.
A duplicate of the original badge will appear in your list of activity badges. Be sure to rename the badge. You may also edit the badge as you see fit for your program. For example, if you want to change the badge image or edit/remove/add activities within the badge, you can simply click on the badge name to edit it directly.
Don't forget to save your program!