Source Code
Stable Releases
There are no fixed releases but branches tied to the corresponding OpenWrt release.
At the time of writing the current stable branch is openwrt-18.06 which is used by the OpenWrt 18.06 release series. See the list of all branches.
You can checkout the branch via Git using:
git clone https://github.com/openwrt/luci.git
git checkout luci-0.12
Development Master
You can checkout the current working branch with:
git clone https://github.com/openwrt/luci.git
or use the Github Source Browser