Sailfish is more open than Blackberry OS. Sailfish is a Linux distro. Blackberry 10 is QNX based.
Blackberry is friendly to side loading like Sailfish so is not unfriendly to you writing applications.
Just the OS itself has more closed components. That is not to say Sailfish is 100% open source.
Blackbery does have some git repos to look at open source pieces.
https://blackberry.github.io/
and let you look at say open browser components
http://us.blackberry.com/software/sm...omponents.html

Sailfish is built on Mer and Nemo which you may jump in and help improve. Lipstick and a few other components are closed, however you may replace the proprietary GUI. You cannot do that in Blackberry.

Blackberry is a great deal more mature than Sailfish and has a larger company behind it along with greater availability but more of the OS is closed. Unlike Apple iOS they are friendly to you writing applications and sideloading.

Of course this is leaving out Android and Ubuntu Touch.