Since this fact is not tolerated on the parent page, it is stated here: there are amateur players who are go book authors, go book publishers, go teachers or earn their income from other go-related activities.
There are, and have been since forever. But it was a completely irrelevant addition to a paragraph about the separation of professional and amateur tournaments and access thereto.
I see. - Would you agree that another paragraph can be added that is unrelated to tournaments and informs about professional go activities of amateurs?
I have no objection to a paragraph explaining that some amateur players make a living from, or derive significant income from, go related activities, such as teaching, writing, publishing, organising or managing. I object to the use of the world professional in that context. So, example:
The word professional is simply loaded in the context of go, and should therefore be avoided to prevent confusion.
Unrelated to go, here is an interesting link showing what it takes, in the US, to be considered a "professional author" for tax purposes: http://publishing.about.com/od/BookAuthorBasics/a/Book-Authors-And-Taxes-Hobbyist-Vs-Professional.htm
In Germany, a Gewerbeschein with its declaration of one's professional activities is required already when having the intention of soon starting them with the aim to later generate income. Tax laws don't care so much for what an activity is called, but simply care for whether the income difference is positive. A hobby (such as playing in amateur tournaments and occasionally getting prizes) is called Liebhaberei. Income must be declared for every activity regularly used for the sake of generating and living from it (e.g., go book writing / publishing or go teaching, if performed in this manner). So, you can see that every country is different WRT collecting taxes.