For instance, when a piece of software is submitted to Debian and purports to be licensed under the GNU GPL, then -- in general -- it is completely unproblematic.
Not quite--because you have to check that it really IS licensed properly and clearly under the GPL. Sometimes the developer *says* this, but when you scan the source files, you see one of them was copied from another package and has an incompatible license, maybe even a non-free license. The situation with the GFDL is not very different. You have to check that the material has been properly licensed under the GFDL, and that includes checking whether non-secondary sections have been designated as invariant. But I see your point that it would be better if we could somehow simplify the job. I will send your message to our lawyer and ask if he can find a way to do that. With the GNU FDL, I don't have any such guarantee. I have to scour the work for Invariant Sections. I think "scour" is too strong a word. The invariant sections have to be listed in the notice that says the work is under the GFDL. Would it be objectionable to the Free Software Foundation if the Debian Project adopted a policy of accepting works licensed under the GNU FDL as Free Software only if they contained no Invariant Sections or Cover Texts (except for narrowly-construed notices of authorship, and the license text)? This would mean you would reject many of our manuals--perhaps all of them. I would be rather unhappy about that. What reasons would I, as a software author, or as a DFSG gatekeeper for the Debian Project, have to prefer the GNU FDL over the OPL? We want to encourage widespread use of the FDL for two reasons: 1. It leads to a pool of text that can be copied between manuals. 2. It is (or at least ought to be) good for helping commercial publishers succeed publishing free manuals. By contrast, the OPL has a major flaw: the two enticing options, either of which, if used, makes the whole manual non-free. You could argue that the GFDL has a similar problem, that someone might declare too much to be invariant. But this is not exactly the same kind of situation, because the GFDL says this is not proper, while the OPL says it is entirely proper.