Well, I think this questions would benefit more people so I'll ask in public: are there any plans for a commercial offering? Thanks!
If these can be added to the free version, cool! :)
Full SSL support, integrated build automation (not just for Jekyll), redirects, built-in performance optimizations, rewrite rules, proxying, fine grained HTTP header control, integration with prerender services, etc, etc...
We can also do custom plans with true DDoS mitigation.
Why not use them to present customer projects (in private repos) to your customers? As long the pages are public this is pretty often a no-go.