I used stuff from http://opengameart.org/ (those with a fitting license only), from https://www.freesound.org/, from https://incompetech.com/ as well as other free stuff that was either free to use by license or I asked for permission. I bought quite a few assets on http://www.turbosquid.com/ as well as on http://graphicriver.net/ and on http://3docean.net/.
…and some models and textures were made by people from the jPCT community.