This app is opensource and is supported by the users paying the PRO license. After the 7-days trial period, if you find that you really like it but cannot afford to the price, here are some ways to get the app for less or even for free (discounts can be added together):
write a review in your native language on the Google Play Store telling why you use this app (50% discount)
share a link to the app on Google+, Twitter or Facebook with a comment telling why you use the app (25% discount per social network)
write a blog post in your language linking to the Google Play Store explaining the value of the app (100% discount)
You just need to send the screenshots or links that prove your actions to email@example.com to get the coupons. Make sure to send them in a single email from an email address linked to your device. I may take up to one week to issue the coupon if I'm out of town or if my inbox is full...