43t34fg4 Or is it all self-hosted from what I'm seeing there?
Yes. As listed in detail¹ in the link from @akc3n the GrapheneOS Project has rented some servers and VPS from OVH and Frantec/Buy/VM. Hosting your own server in colocation is significantly more expensive. (If you don't get it sponsored, like me for example.)
¹It's rare to be so open and detailed.
43t34fg4 Both of those (there's 3 total) are just for the site itself? How's that work?
Content Delivery Network (CDN)