Note that there is not a requirement that they make their source code public, only that they provide source code to users who have received binaries. This means if this app is GPL licensed you can buy it and make a written request for the source code, and they are required by the GPL to provide it.

There is also not a requirement that the binary made available gratis. “Free” in free software or FOSS is about freedom, not price. This is a common misunderstanding of both terms.