You can get the SDK (fireprime_android5.1_git_20150612.tar), a 6.1GB download with full source code for the board via Baidu or Google Drive, and then upgrade it to the latest version with git pull on the company’s bitbucket account as explained in the Wiki. The SDK must be specific to Fireprime board, but it should be feasible to use to create / modify Android 5.1 firmware for other RK3128 products.
If you don’t need the source code, but would just like to install the firmware for Android 5.1, and the other image recently released (Ubuntu 15.04 Desktop or Server, or Android 5.1/Ubuntu 15.04 dual boot image) via the links provided in the announcement.
Thanks to Nanik for the tip.
Jean-Luc started CNX Software in 2010 as a part-time endeavor, before quitting his job as a software engineering manager, and starting to write daily news, and reviews full time later in 2011.