New Polybrush version (all updates are free)
Now all brushes stored at server, you can use brushes of other artists. Brushes are downloaded automatically, it doesn't affect program work (you can use it offline)
Of course you can mark your brushes as "private" and don't share them with others.
There also brushes sorting by tags and new ability to create brushes from images. You can use any image instead of mesh as brush form.
http://polybrush.org/