I'm actually still really excited for this. It runs Qt, HTML5, and Android apps. Sure, it's not trying to create a new convergence story like Ubuntu, but its interface is much more sensibly designed. Also, Firefox OS is cool, but they really went backwards from their initial designs- it looked much more interesting before the carriers got involved and took away the polished theming and home screen. So I'll probably stick to Sailfish, so long as we get some phones with it. Oh, not to mention it runs on X11 and soon Wayland- not SurfaceFlinger.
Closed source? It's Mer core you can send how many patches you like and build the source your self.
In the beginning Jolla said that there UI will have some closed elements but it will be compatible with nemo (the UI is radically different).
If you want total open source you should use Mer+Nemo instead of Sailfish OS, the choice is yours.
Jolla contribute upstream and tries to be as open as possible and to give back freedom to the users.
About patents ofcourse Jolla will need some patents, how else could they compete in the smart phone market?
Patents might not be by choice it's forced on you in the smart phone manufacturing business.
Sailfish is the one of the new OS that i have highest hopes for.