The C25K Starter Kit is a bundle of free apps that are all part of the Zen Unlimited Pass. This is a free download.
You will need to subscribe to the Zen Unlimited Pass to access pro features across all of those apps.
The Zen Unlimited Pass includes:
– Unlimited music streaming
– Calories and distance tracking
– Unlocks 10K Trainer, 13.1 half marathon and 26.2 full marathon training programs
– Access to pro features in all future Zen Labs apps