Hi Ashley Cowell-Haskin. Welcome to Grokker! Great question. Currently, all users are only allowed to join one program at a time. However, even if you are involved in a program, you are welcome to do any other videos from Grokker.
Here is a suggested work-around to be able to do programs at one time:
1. Join the program that is the longer of the two that you are interested in doing.
2. For the other program, manually add each workout to your calendar, following the recommended schedule in the program.
This does take a little work to do it this way; however, both workouts will be on your calendar and you will receive reminders on when to do them.
Hope this helps. Please feel free to reach out with any additional questions.