Not necessarily. The clause only seems to apply to the binaries provided on the iTunes or Google Play store, and not to the actual source code, which is BSD licensed [1], or any binaries you might build yourself.
I am speculating that the clause is intended to be part of the Keybase terms of service, but because the software and service are tightly coupled, it is phrased as a software license restriction.
I am speculating that the clause is intended to be part of the Keybase terms of service, but because the software and service are tightly coupled, it is phrased as a software license restriction.
[1] https://github.com/keybase/client/blob/master/LICENSE