This was true for a long time but not anymore. As far as I can see, at some
point (not too long ago) the pressure was too big and they released a version
independent from gapp (several people made forks, some using Signal(TM)'s
brandname and these were threatened with legal action). An official apk is
now available through their website and it is independent of gapp, though I
think they say somewhere that it is not recommended.
From the little I know, Marlinspike (OWS founder) looks down on most others.
At some point I remember he claimed he would not create a non gapp dependent
version because he would not have all the download and usage stats that
google provided his company (aside from defficient push notifications).
He does not hold the free software community in high regard and is happy to
collaborate with all the largest digital monopolies. As I remember he also
claims to be an anarchist.
Having said all of this and from a purely utilitarian point of view, Signal
has provided an easy-to-use platform for non-technical people. It is a shame
they would not make any effort for the technically capable, ethically
concerned users. I hope a federated version run by down-to-earth people will
be available and will achieve at least similar userbase among non-technical
users someday.
On the upside, he seems to be a good coder and there's been at least one
independent audit at Oxford Uni that found no major flaws in design. OWS's
work has probably made government mass surveillance more difficult on every
platform that uses Signal's code (Though who is to say what code Facebook is
actually running or whether they've introduced backdoors).
The following thread is a request to include Signal on f-droid and is quite
enlightening of Marlinspike's (username: Moxie) attitude toward free
software, federated networks (XMPP and Chatsecure in particular), monopoly
corporations and his peers:
https://github.com/LibreSignal/LibreSignal/issues/37
