Open source doesn't mean the source must be publicly available for everyone to read. :)

That's exactly what I thought open source meant. How can a source be open if not everyone can read it? I didn't get your comment.

Open source can mean that the source is available on request, or is available after purchasing a licence. It doesn't have to be publicly available to be open source, though in practice it pretty much always is.

True :) I've just come to think Open Source == FOSS

Even with the GPL, the source doesn't need to be publicly available for everyone to read. Only paying customers are guaranteed the right to the code. (Some car makers have GPL software and only give out the source code to verified car owners.)