Git is a registered trademark, I don't see notice of permission… maybe they didn't ask and might not have it?
Also, it's entertaining to me that in one comment you say that closed-source proprietary software is bad, and in another comment you're concerned about whether they follow trademark law. I understand that it's not a direct comparison and open source software is still subject to IP law; it's just that the juxtaposition of your comments is a bit silly.
Copyright is a restriction that mostly censors the sharing and building of ideas freely. It should be abolished. But it's currently used to deal with plagiarism and to support copyleft licenses. We should have stronger legal protects for attribution, against false endorsement claims, and support technology freedom with mandates for source release for published works and prohibition of DRM.
Patents are just bullshit. We should abolish patent law and just have better social systems for grants and funding for research (although it might already be true that almost all useful patentable inventions are built on socially-funded research already).
Trademark is a consumer protection. It is absolutely essential. It protects people in the market to know that they are dealing with the same legitimate entity when they see the trademark in use. There are cases of abuse or of it being overly strong, but trademark is totally important and basically positive.
Also I have the feeling that if they had permission that they wouldn't forget to add a notice about it to the bottom of their page.