What should be selected in order to store a pose? I've a mhx rig (created with makehuman) when I select fingers and 'links' and store a pose in a pose library the pose can't be assigned. 
With other poses arm/legs (set to IK) etc. this works fine.

What should I do to store the pose of the fingers (Could the bones to select be in a different layer)?

Note: Selecting and keyframing the bones works. My goal was to script poses from a control file to  keyframes. I didn't notice that the NLA-Editor was made for tasks like that.
Not familiar with the MakeHuman rig specifically, but generally speaking, on a sufficiently complex rig, you typically have control bones and deformation bones. You only set keyframes on the control bones... this is both in animation as well as building a pose library. Judging from your screenshot, I'd say you should only set keys on the larger, L-shaped finger bones and not the bones located within the mesh geometry. Those should remain hidden in nearly all cases.