https://pixologic.com/zbrush/downloadcenter/alpha/ is arguably one of the best resources for sculpting alphas.
The TOS of Pixologic permits the use of the library for whatever purpose, commercial or otherwise, using any software, as long as you do not distribute the alphas themselves to others. This condition would prevent Nomad from bundling the alphas in the app, or acting as any kind of middleman. It, however, doesn’t mean that Nomad can’t make it much easier to import these alphas. The problem right now is that they come as zipped psd files if you download them from the site, which makes it a chore to import them into Nomad. I think it would be awesome if Nomad could directly use these zips.