Is your translation tool developed internally or do you use a 3rd party site/service? We would be interesting in implementing something similar for our software product.
To clarify, are you referring to the MarkdownPad Translation Project site?
Yes, the MarkdownPad Translation Project site.
We're using GlotPress for the back-end. The setup and installation isn't super-friendly, but it's open-source and is hosted with SVN: https://glotpress.trac.wordpress.org/browser