a) Google can read JS, but they can't necessarily navigate through all the different pages of a single page app. Their recommendation for that is currently to use #! and then when GoogleBot visits a page and sees the #!, GoogleBot will replace that with ?escaped_fragment=... It's then up to you to provide the content of the page to GoogleBot, and that is what this service appears to do.
b)As long as you are serving the same content to Google, it is not considered blackhat seo, and you won't be penalized. Cloaking would be serving different content to Google than you serve to the user in an effort to boost your rankings over what the content the user sees would rank.
At SEOMoz,no? But that shouldn't matter - I could see a few ways you could gain large market share. It's clear to me that SEOMoz, large SEO firms, major/minor search engines will either build or acquire something like this. Some thoughts on large account acquisition strategies and revenue...
Account acquisition
For SEOMoz - Try a few channels in the door. A) More aggressive/direct - Contact a junior salesman, and sell him. Offer him a referral fee for anybody that uses Angular, etc that he refers. THen try that with each, and approach the head of sales. B) Less aggressive - Follow their blog, and find the key SEO thought leaders in their company or that guest blog. Those are influencers, contact them and offer them initial access. C) Partners - do the same for each of their partners. Investigate their entire client lists (eg: maybe linkedin, etc...offer it for free or reduced - and then leverage that for sales).
For major search engines (Google, Bing, DuckDuckGo) - Offer directly to them, their staff, sales staff to partner to do SEO for angular apps and feed that to the search engines for free (or as a service initially of your time). Have their accounts pull you in. Partner with head SEO influencers, or Google partners. Then use that to approach Google/DuckDuck's staff saying "We already do SEO for 30 of your angular app customers".
For growth hackers - Focus on growth hackers, do cross-promo with them offering special deals. Get them to pull you into the major startups they're at.
For major SEO Firms - similar partnering, sales startegies as above.
Revenue
Offer a few tiers, initally to the larger marketing agencies, do it as a service. THis would give you enough revenue to bootstrap (eg: a couple $k per month for a few clients).
Approach a few well known, high grossing startups you know are using Angular, etc and offer to either do it as a service, or to partner and do it for cheap for marketing.
All of these are worth the price you paid - your mileage may vary.