I have developed an Android application that makes use of some GPL source code developed by someone else. Now I would like to release the application to Google Play. I understand that I must release full source code of the application under GPL, but I would like to do it for a fee, and I know that GPL permits it.
Now, what if a potential user wants to try the application before buying it?
To resolve this issue, I thought to release the application in 2 versions: - TRIAL version, with full functionalities but for evaluation only, downloadable for free; - FULL Version, with source included, downloadable for a fee of 100$ or so.
My question is: does the GPL permit to release a DEMO/TRIAL application for free but without source code, so that the potential user can try before buy?