Has Anyone Heard of This Book?

[Alternate]

A long time ago, I owned a good sci-fi book. I was really young when I read it, so I didn't understand it very well. Now that I'm older, I realize it actually seems like a pretty good book with moral points, so I'm trying to find it. But I can't remember the name, or author, or anything. I tended not to care about memorizing titles back then. Lol. I can barely remember anything about the plot.

At some point in the future, mankind entered a golden age of technology in which they were able to colonize various foreign planets. Planets which couldn't be inhabited by humans, they created cloned, inhuman variants to send there.
Then, conservative extremist groups, angered by "evil" scientific advancement and inhumans, essentially destroyed the planet with nuclear weapons or something.
The colonies were isolated. Those that were able to survive lost contact and technology, and began to develop unique cultures.
I think the book takes place a few hundred years later, after several of the colonies start to re-create ancient technology and head back into the galaxy to re-find each other. By this time, each inhuman (and human) race has become very distinct, with differing ideals, technologies, beliefs and conflicting cultures.
The plot starts when a genetically-engineered supervirus starts wiping out the newly re-united inhumans and humans. The characters are from various species, and they try to work together to figure out who created the virus and stop it before it kills everyone.
It turns out that the creator of the virus is the original (presumed to be extinct) human race from Earth, which has, like the colonies, recovered from near-destruction. Earth is a massive theocracy controlled by religious fanatics who now want to exterminate organic/genetic science and diversity in their former colonies. (Many of which range from agnostic to atheistic.) And the colonies have to choose sides and unite to survive and destroy Earth. Again.

Does anyone know any books that sound like this one? I haven't been able to find anything on google about it, but I'd really like to read it again.