Previously, you had to be an Adobe Creative Cloud subscriber to make use of Lightroom Mobile for Android. With the new version 1.4 available now in the Google Play Store, Lightroom Mobile is free to use.
Of course, you’ll still not be able to sync files with your desktop Lightroom library, but you can edit, rate and export local photos to your heart’s content on your Android mobile device. Since some Android devices are now supporting DNG file formats, you can also do raw editing with those DNG files in Lightroom Mobile for Android.
For iOS users, Adobe opened up Lightroom Mobile for everyone in version 2.0 released in October of this year. You can find it here in the App Store.