LineageOS is based on the Android Open Source Project with extra contributions from many people within the Android community.
It can be used without any need to have any Google application installed.
Linked below is a package that has come from another Android project that restore the Google parts.
LineageOS does still include various hardware-specific code, which is also slowly being open-sourced anyway.
The source code for LineageOS is available in the LineageOS Github
And if you would like to contribute to LineageOS,
You can also view the Changelog for a full list of changes & features.
LineageOS, ROM for the OnePlus 2
Seraph08, Grarak, TheCrazyLex, Mahdi786
OP2 Device Tree
OPPO Device Tree
ROM OS Version: 8.1 Oreo
ROM Kernel: Linux 3.10.108
Based On: LineageOS
Last Updated 2018-02-20