It's one thing to take advantage of open source software, but it's another to contribute back to open source. The point of this page is to show the latter…
Yes, that may be so, but perhaps (in some cases) it is because they feel legally obliged to:
"This repository is published in order to share code and information and is not intended to be used directly outside of Twitter. We provide no guarantees of bug fixes, ongoing maintenance, compatibility, or suitability for any user outside of Twitter"
