Apps these days are just web browser wrappers. The code is not in the app but rather inside the actual web servers. So releasing the source code would do little.
Not all apps are like this and I'm not saying this one is in this case....I really don't know which way it is for WU. But I'm just saying it may just be that it all resides on the web server. Netflix is that way (in the cloud), and YouTube (Android TV), and Amazon is that way to name a few.