The Android installer installs the whole ET: Legacy universe. It will download the original Wolfenstein: Enemy Territory assets if they are not found on your computer.

• Get the Android installer.
• Run it!

With current master: You will find your etkey, profile folder and all downloaded files (such as custom maps and mods) in the ExternalPublicDirectory ExternalStorage/Documents/etlegacy or /storage/emulated/0/Documents/etlegacy directory. You can upload/delete/create in this directory without any restrictions.

It is not available to download. But you can use 7zip or any other archive tool to unpack Android Installer.