Hi Kathleen Holland. Welcome to Grokker! At the current time, a user is only able to join one program at a time. This is a feature that Grokker is looking to change in the future. In the meantime, I can give you a workaround:
1. Join the longer of the two programs
2. Then go to the program page of the 2nd program you wish to complete.
3. Manually add these workouts to your calendar, using the schedule set in the program.
While you won't be officially part of this program, these workouts will show on your calendar and you wll receive reminders about them.
I hope this helps. Please let me know if you have any additional questions.