The premium version has the same features as the free version, plus:
It allows you to define 16 GPIO inputs or outputs (for example, you may define 8 GPIO outputs and 8 external sensors, or 16 GPIO outputs for relays).
It allows you to create battery-powered DIY devices with effective power management.
PCF8583 counter, PCA9685 multi-channel PWM, Real-time clock, Cron scheduler.
5 hardware built-in PWM apart of of 4 PWM in the free version.
Hardware PWM with low frequencies.
I plan to add new features and sensor types to the premium version.