Develop a trial version of a GPL program [closed]

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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?

Answer 1

http://www.gnu.org/licenses/gpl-faq.html#DoesTheGPLAllowDownloadFee says:

Yes. You can charge any fee you wish for distributing a copy of the program. If you distribute binaries by download, you must provide “equivalent access” to download the source—therefore, the fee to download source may not be greater than the fee to download the binary.

Which I take to mean that the source code for the TRIAL version must be made available for the same cost or less (free).

Furthermore, don't forget: http://www.gnu.org/licenses/gpl-faq.html#DoesTheGPLRequireAvailabilityToPublic This means that someone else can take the source after paying one million dollars, compile it and distribute it. I believe this is how CentOS works.

By using RedHat as an example, the key would be first-to-market backed by support. People could re-share your source but they would have to bother. If your product is good and you continue to keep it fresh, then the risks of clones is reduced.