Pootle has the ability to display an alternative source language while translating. Thus, translators who know another language better than English can take part in the translation project. Also, it provides a way to dissambiguate terminology seeing how other languages have translated the same translation unit.
Since version 1.3, it is also possible to define multiple alternative source languages.
In order to have this feature available, it must be enabled by the Pootle server administrator (disabled by default). See pootle.prefs for reference.
Users who want to use the functionality need to specify the desired alternative source language in their options page. If “None” is selected in the drop-down list, the feature will be disabled for the current user.
Note that if the selected project doesn't have the alternative source language it couldn't be displayed.