Why would it be? It's the same as the GPL, only difference is: modified version sources must be available to remote-network-interaction users. I don't see what's restrictive for business.
If you go and sell somebody a hosting solution based on Nimbus, you'd need to share your source code.
What I'm not sure of, is if you build, say, a photo sharing webapp using Nimbus as the storage back-end, does your webapp become AGPL by linking? I'm fairly certain GPL would require this, but, as per the rationale for AGPL, you don't care about that when you run a webapp.
Curiously, if Nimbus adopted the exact S3 API instead of "similar to", it would not constitute linking, as it's using a standard interface.
