When you apply the License Key from the Advanced Settings of the App. The water mark goes away. This is true when you use AppRun (run the app from the desktop) or run the build app on the device. However when running from Player it will always be watermarked. This is an expected behavior. I have licensed my app but on Player it appears like this.
When running in AppRun (from desktop) there is no water mark
If you checkout the About page in the Player it is mentioned that apps with Runtime 100.1 will always have a watermark.
We will include this information in our doc in next release as an enhancement.
Thanks,
Nakul