I second this. If a kickstarter for free CCNA classes can get funded, why not a project like this? As long as the right people see it, it will get funded.
As for editions, my vote would go to pricing based on the amount of devices monitored (<50 = free version, >50 paid, Plus direct support, API, More features?).
As the prices, I have no clue what would be good. To me personally, I use this to monitor my home lab (about 10 items), and I would have no problem paying $20-30 yearly. I know that's a low price, but then again I have very few devices, and anything more would push me away. If I feel this way, chances are others do as well, and this is why I think pricing should be based on the number of monitored devices.