I think Rockwell will be able to use a different server, but as the server name is likely to be embedded in the app, even after organising a new server as the buffer for sotawatch spots and to generate the push-notifications, he will need to submit the new version of the application to Apple for verification. That usually takes a while to be processed so even if he has a fix today, it could be a few months before a new version becomes available on the App Store.
In the meantime, as mentioned already, it is possible to subscribe to a Twitter feed notifying new sota spots. It doesn't have band and mode filters, but it might be better than nothing.
Re donating to the server cost, that's a good idea. Let's ask Rockwell how best to do that. The simplest is just to pay a fee for the app. I'm up for that too.
73 Andrew VK1DA VK2UH