Integration with other translation tools, like desktop PO file editors (Virtaal, Lokalize, etc.), web based translation tools (Pootle, Transifex, etc.), can be done by exporting and importing translation files. It can be done on the web interface, from the dashboard of a project. But it can be done from the terminal as well (if you have access on the server).
This is how the commands look like:
In the vocabulary mobile app (http://v.btranslator.org) I have implemented what I call translation in context. It works like this: when the user makes a Ctrl+Click on a string/translation anywhere on the UI, a browser tab/window is opened automatically with the correct url in the translation server (web application), where he can give a translation or a new suggestion for the selected string. Of course, for a normal Click the UI works as normally it should.
A translation project is composed of some POT files (PO template files, with extension .pot) and some PO files (.po extension) for each translation language. The name of the PO files should match that of the template (POT) files, except for the extension. New projects on B-Translator can be added both from the GUI or from the command line terminal (if you have access to the server).