It's a little more than an F-Droid warning. I am, probably unnessessarily to be fair, afraid AOSP might disappear one day - or be crippled so much that upkeeping things like Lineage or Calyx or alike is made intentionally hard to impossible.

Which would effectively lead to "killing" (i honestly am too braindead for a better synonym right now) those ROMs. Which would be bad...