Hi Lindoz,
The 2000 and 907 styles were all freely available and by no means are all of them based on songs, many are just the standard Yamaha simple 2 and 4 measure styles.

Yet Yamaha lawyers insisted that the user groups remove the styles of the new keyboards purely from their own commercial interest point of view. Thus there must be some legal ownership for them to do this, otherwise the user groups could just ignore them?

It looks like Yamaha want to offer styles (but only from the older products) at their own web site, so this move was to strengthen their own position in this regard, and just to prevent others from offering the Yamaha styles.