The costs of running a Send server probably exceed those of its source code alone, which makes it a tricky proposition to say "here's the source code" alone. I'm not familiar myself, but I imagine it looks the same as any other public non-P2P file sharing service:

- Webapp & hosting costs

- Data storage & transfer costs

- Copyright & Abuse response costs

Yes, but those are business challenges. Some handle it better than others, Mega seems to be doing it with a fairly small staff.