1) I don't know non-free network either....2) They use non-free software on their servers, it's not really a deal breaker (otherwise it....wouldn't appear in F-droid), but I don't mind a big warning sign. F-droid feels that it's worth noting, and they've got the right to.
What they rather shouldn't do (which they don't) is unaccedentally excluding Telegram from their repos on the basis of that, in my opinion.
So all is well.
