I think that requiring a credit "at least as prominent as the credits for the other contributing authors" for a small contribution is requiring excessive credit. That's why I consider this clause as a non-free restriction. As I said, if the clause said "at least as prominent as the credits for the authors of other comparable contributions", it would be OK, but the actual clause doesn't say so, unfortunately.
Okay, I'm thinking of programs here, but I've come across several projects that, when they rev the program, drop the credits of authors of the previous version into a credits file.
Given that linux replaces a considerable amount of code at every iteration, and other projects probably do the same, this seems fair. However, this clause, to me, seems to forbid this practice.
Indeed, the "drop credits into a file" approach may be a very fair way of thanking authors whose work has been completely rewritten and who therefore no longer have any right to credit in the current work but who deserve credit because it was their work in the original instance. With this clause, how can you be fair to people like that?
Cheers, Wol -- Anthony W. Youngman - anthony@thewolery.demon.co.uk