I forgot that CPAN-cpan uses CPAN::SQLite, cavac, but CPANPLUS-cpan appears not to:

$ perl -w -MCPANPLUS -le'print "$/$_" for values %INC' | grep CPANPLUS
+ | xargs -l grep SQLite
                    'DBD::SQLite'  => '0.0',
                        eq 'CPANPLUS::Internals::Source::SQLite'
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As you see above I did a quick-and-dirty grep peek into CPANPLUS and it uses DBD::SQLite.

Edit

I've done a bit more poking around in the code to see if I can get cpanplus to use SQLite. I discovered that the line found above by grep, 'DBD::SQLite' => '0.0',, is preceded by the line containing 'DBIx::Simple' => '0.0',. I installed DBIx::Simple and the result is that when I make test on CPANPLUS it seems happy to use SQLite. Here's a part of the code I'm talking about, in /CPANPLUS/Selfupdate.pm:

            sqlite_backend => [
                {   'DBIx::Simple' => '0.0',
                    'DBD::SQLite'  => '0.0',
                },
                sub {
                    my $cb   = shift;
                    my $conf = $cb->configure_object;
                    return $conf->get_conf('source_engine')
                        eq 'CPANPLUS::Internals::Source::SQLite'
                },
[download]