The Swim Team plugin is spread across 93 PHP source files and is roughly 70,000 lines of code. Messages are spread throughout the plugin – the are defined where needed.
There are a bunch of constants defined which would be easy to setup for translation but that is a small minority of the strings used in the plugin. As I noted, I started work on this plugin about 7 years ago. At the time things like Custom Post Types didn’t exit although having dome some work with CPTs, trying to use them for the Swim Team model would be very difficult.
Initially I developed this for our local neighborhood swim team and didn’t expect it to grow to the extent it has. There was always a long list of things our own team wanted to do in addition to the requests I got from other teams who have used it. Unfortunately, translation was never a high priority and was something I figured I’d deal with later.
Now that I no longer have any swimmers in my family, I am not doing any major development on the plugin but it is largely feature complete at this point and works pretty well.
I plan to move it over to GitHub so people can fork it and that would be the best way to contribute to future development and I will get to doing that one of these days. If this is something that would help you out, let me know and I’ll move it up my priority list.