GApps packages (short for Google Apps) are essential in the custom ROM development community. The reason why GApps are not bundled with custom ROMs such as LineageOS is that while LineageOS is an open-source Android distribution, Google apps are not open-source. Apps such as the Play Store, Gmail, Maps, etc, do not use the Apache or GPLv2 license. Therefore, custom ROM developers can't bundle them with their builds, as doing so presents legal challenges.
Open GApps Now Supports Android 8.1 Oreo (ARM+ARM64, x86+x86_64)
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