I thought the next paragraph was much more interesting:
"If you are an existing developer of client apps, you can continue to serve your user base, but we will be holding you to high standards to ensure you do not violate users' privacy, that you provide consistency in the user experience, and that you rigorously adhere to all areas of our Terms of Service."
Translation: "we will be looking very hard for any excuse to shut down existing unofficial Twitter clients."
I can't imagine that Twitter's service adds enough value to any 3rd party developer that scraping would make any sense. I think Twitter's doing irreversible damage to their developer community.
Wether or not that backfires on them is yet to be seen.
"If you are an existing developer of client apps, you can continue to serve your user base, but we will be holding you to high standards to ensure you do not violate users' privacy, that you provide consistency in the user experience, and that you rigorously adhere to all areas of our Terms of Service."
Translation: "we will be looking very hard for any excuse to shut down existing unofficial Twitter clients."