Drupal is kindof database independent. Though no-one has managed to integrate sqlite because of 'things' (locking) that Drupal requires.
My hopes are that SQLite support will happen with Drupal 6. Tadej Baša has written the code and he says he is running Drupal with it since 4.5 which is quite believable. He also volunteers to be the maintainer: http://lists.drupal.org/pipermail/development/2007-January/021806.html My hopes are that Drupal will run out of the box, without any setup whatsoever. LOCKs are on their way out, killes is nurturing the no lock patch I abandoned. And even if they do not die, they are there only to avoid some races which simply do not happen on the small sites that are targets for SQLite (ie. quite small sites).
Would using foreign keys and dependign on them not narrow the posibilities for other DBAs a lot? And do we care?
We will not depend on them as MyISAM happily ignores FKs. Regards, NK