AICP is known by everyone as the "Ice Cold Project" that started on a Desire HD years ago (2012) and since then has evolved into a mature ROM with the BEST community that you can find!!!
Until Android Lollipop, the ROM has always been based on AOKP. Unfortunately, since AOKP stopped development (but made a comeback later), we changed our base to CM.
With the re-brand of CM to LineageOS (LOS) we became LineageOS based with some tweaks from AOSP and we are now based on the "Ground Zero Open Source Project" (GZOSP) for Android Pie.