This issue is tracking for gem release of DBM module.
#4 [ruby-core:79789] Updated by shevegen (Robert A. Heiler) about 1 month ago
Perhaps the rubygems.org folks can de-register that gem, due to two reasons - ruby stdlib and core should have a higher priority over custom gems; and the gem is not very active, only two updates, one in 2009 and another one in 2013. (It seems to be jruby specific. Perhaps it could actually be integrated into jruby itself as-is.)
In the long run, optional namespaces/authorship-registries for gems should perhaps be added (and multiple same-named gems could be made available at rubygems.org, though of course then gem also needs a way to install same-named gems from different authors). All gems in ruby stdlib etc.. could have a registry such as "ruby core" or some similar identifier to keep track of the gems that are currently available, at the least in the latest ruby release; the gem commandline interface should then be able to pick up that information and notify the user of possible name conflicts. But anyway I digress - IMO ruby core should have priority over other gems at all times.