The software is pretty much already announced: Laravel 5, with Twig for tempting. Both have already been announced
If you mean the requirements, PHP 5.4 and MySQL 5 or postgresql. Front end wise, it's jQuery running the JavaScript at the minute, and we're using SASS to build the default theme, with gulp.js to mange builds. This will likely change, as we plan to have some system to manage assets via the ACP, including JS scripts.
