Are you suggesting that such restrictions are acceptable under the DFSG, or are you suggesting that such restrictions might be beneficial and thus we should adapt the DFSG to permit them?I firmly believe that the former is true. GPLv3 Affero-style clauses provide a minor restriction on modification that is designed to provide the users of software with source code and the ability to modify that code.
I believe the goal is noble and in the spirit of copyleft, and I also believe that the reason there is no example of a DFSG-free license that implements it is because it's impossible.
Fundamentally, the whole idea is worthless without a use restriction, not just a modification restriction. Even if we forgot that limiting the types of modifications allowed is non-free, the restrictions necessary to make actual running systems behave as desired are ridiculously non-free.
Here are some cases to keep in mind when designing such a clause:1) works derived from both AGPL and non-free sources (say statically linked or actual source commingling with a non-free TCP/IP stack). Under GPL, these systems can be created and used, but not distributed. AGPL makes them completely illegal.
This gets to the quesiton of "full source code". This is (mostly) clear when talking about distributing source for objects you distribute. It's not at ALL clear which source code must be distributed for a running service.
2) someone leaving in the feature that allows a "user" to get full source, but only running it on a system where the feature is irrelevant (kiosk, or just firewalled to block the source-retrieval URL).
3) who exactly is a "user". This is not an easy definition. If I use a browser to hit a page that says "403 access denied.", am I a user? If I look at a page over my friend's shoulder, am I a user?
It really comes down to "the requirement is meaningless because it's trivial to work around, or the requirement is far too invasive and non-free."
-- Mark Rafn dagon@dagon.net <http://www.dagon.net/>