How to translate Boolean field labels?
I'm relatively new to Drupal but I've had the same problem recently and this is how I solved it:


install the i18n module and enable the "field translation" sub-module (and its dependencies).
in the boolean field settings (admin/structure/types/manage/[your-content-type]/fields and click the edit link next to the field) make sure you have specified a value for the On and Off states (e.g. Yes/No).
then on the same page (boolean field settings), use the translate tab (on top of the page) and click "translate" for each language you need: 
under the Field instance tab, you can translate the label for the field.
under the Field settings tab, you can translate the values for the On/Off states. 
lastly (and this is perhaps the less obvious step), go to manage display (for your content type), and as "format" for you boolean field, choose "Default translated" instead of "Default".


Hope this helps.