[OSM-talk] Can I say "yes" to the ODbL if I can't account for 100% of my data?

[Ævar Arnfjörð Bjarmason]

Back in 2006 I wrote the following when it still wasn't clear what the
ODbL acceptance terms would be like:

On Sun, Dec 6, 2009 at 22:10, Ævar Arnfjörð Bjarmason <avarab at gmail.com> wrote:
> If someone presents me with a boolean "Do you allow relicensing under
> the ODbL" I'll have to say no because some of my edits are derived
> from CC-BY-SA data I don't have permission to license (and I probably
> can't even recall what all of it is).
>
> Which'll mean nuking >50% of all the data in Iceland most of which
> I've touched at some point.

I've been away for a while. But it seems to me from reading the terms
that I can't say yes to them in good faith, not because I don't want
to, but because I remember I derived a few things from external
CC-BY-SA, and I can't now recall what they were (and this was before
we had changeset comments).

What are my options in that situation? Do I either have to see all my
work removed because I can't account for 100% of my edits or lie on
the ODbL acceptance form?