It depends how you interpret "but hasn't made the source code available" .
Usually source code is available live-on-the-web or ftp and this is
preferred, so people can download and examine it with no waiting.
It is not a requirement of the GPL that source code be live, only obtainable.
This means 'available on request'.
If the author refuses a request to send a copy of the complete source code
that is under the free licence or they are uncontactable, the program is no
longer considered to be Free Software.
This paragraph is from the wikipedia GPL page:
https://en.wikipedia.org/wiki/GNU_GPL#Copyleft
Many distributors of GPL'ed programs bundle the source code with the
executables. An alternative method of satisfying the copyleft is to provide a
written offer to provide the source code on a physical medium (such as a CD)
upon request. In practice, many GPL'ed programs are distributed over the
Internet, and the source code is made available over FTP or HTTP. For
Internet distribution, this complies with the license.
