[ruslan]

brlcad.org says it's both CSG and B-REP.

Although BRL-CAD is powerful, it is still a collection of tools, not a solid application, which makes it pretty hard to use and to comprehend for a regular CAD user (designer). From their website:

BRL-CAD is a suite of more than 400 tools and utilities. The suite of applications are intentionally designed to perform a succinct task so that they can be chained together, scripted, and expanded upon in order to provide powerful flexibility.

I think someone has to develop a decent GUI for this package to make an alternative to FreeCAD.

[RobotToaster]

It seems like a really powerful application, but it's main interface looks like it was written in the 80s, because it was. It's a real shame.