Re: Dependence on nonfree software

[Svetlana Tkachenko]

> "A different case is when the program talks across a network with
> a server running on another machine, and the server is proprietary or
> has an unknown license; unless the two pieces of software make a
> single program (for example because they exchange complex data
> structures intimately), the client does not really depend on the server.
> In such scenario the user is not required to install nor run any
> proprietary software on per computer, so there's no dependency of
> the client on the server, even if the server's responses are needed for
> the program's main functionalities; said client program is therefore
> eligible for hosting."

This can become dangerous: the free software ecosystem may begin to 
depend on software that talks with proprietary servers with no 
documentation about how they work, other than the properly licensed 
free source code.

This may become more difficult if the proprietary server API changes
quickly, nearly every day. This becomes a problem: while it does not
force the users to run proprietary software, their existing free
clients for this server may break easily, and not all maintainers will
be able to resolve this quickly.

Does this seem similar to "service as software substitute"? How to 
quantify this or what barriers would need to be added?