Piwik Mobile 2 is built using Titanium Mobile SDK which is licensed under Apache v2. It gives us the possibility to build native applications for Android, iOS, BlackBerry and Tizen as well as to generate a mobile web application from one code base. The code is written in JavaScript. If you’re German speaking you might want to look into the book Titanium Mobile – Multi Platform Apps using JavaScript which is written by Thomas, the developer of Piwik Mobile 2. It gives you a great introduction on Titanium Mobile.