The pro version is a bit pricey, for an open source app and for something most people will only use on occasion. Also an app like this doesn't do much so I wonder why limit it by locking-away some features.
SkySafari is a better app for actually doing astronomy, but the pro version is quite expensive, and each major version is a new app that you have to pay for again if you want to upgrade. I bought it a few versions ago and still use it regularly.