It's ok if I will sell the compiled and ready to use applications in binary form but provide access to the source code of this applications? For example, I want to sell my own VST plug-ins developed using JUCE and to comply with the GNU GPL license, I will provide end-users access to the source code. Do I need in this case buy a commercial JUCE license?
The problem with this model is that anyone can just grab your source code build it and then sell it for $1 less or even free. I don’t think such a model will work in the long run.
Ardour is one application that is using this model: http://ardour.org/
They release source code and demo binaries for free, but if you want the unrestricted binary you have to donate at least $1.
They also have several hints during the application runtime to "shame" people into buying it.
(like if you render a song with the demo version).
Ok... And what if I will provide access to the source code for buyers, after an explicit request from them? In this case, whether it would be a violation of GPL license?
[EDIT] The JUCE license allows you to sell closed source software, and the GPL license allows you to do whatever you want as long as the source code is available and as easy to access as the binary. You will not need to register for a license if the source code is available next to the binary.
If he chooses to release the binaries as GPL (thus having to provide source) he doesn't have to buy a juce comercial license because he's not using it.