In Civ4, the barbarians actually would develop, just (usually) slower than the other players. On rare occasions they'd even complete Wonders.
Depending on what exactly you're going for, some other ideas would be giving them different units (ex. cheaper, but perhaps weaker ones, or workers that could only do certain worker tasks, such as not being able to railroad), and perhaps giving them unique buildings that produced less culture or no culture. The latter likely would be possible by giving the barbarians a unique government (with a non-researchable prerequisite technology that only they started with), discouraging them from other governments via setting the flavours for Monarchy/Republic/Democracy/Communism/Fascism to exclude their flavour, and setting them to shun Feudalism, and then making the barbarian buildings require their government, and set building flavours to favor barbarian buildings for their flavour.
The caveat is that while that would exclude non-barbarians from building barbarian buildings (due to not having the barbarian government), it wouldn't totally exclude barbarians from also building non-barbarian buildings. On pre-built maps, you could probably do that for the most part by requiring a "civilized" resource that you could pre-place on the map where civilized players were located. By also making that resource require a technology that only civilized civilizations were granted (and could not be researched), I think you could ensure that barbarians could never build non-barbarian buildings, even if they captured a civilized capital (since culture buildings are destroyed on capture).
A lot of this is rather theoretical, but I'd be curious to hear if it does work in practice as well as in theory. If it does, it avoids the perhaps less-desirable option of creating separate tech trees, as Firaxis did in the Middle Ages scenario.
