Yes, that is correct with the new Acresso Software Licensing system that is included in the Autodesk 2010 programs. So if you need to have AutoCAD Raster Design 2010 you will need an AutoCAD based application that has the same Licensing system.
You have a network version of AutoCAD 2010. Then you must have a matching network version of AutoCAD Raster Design 2010. However, if you have a standalone version of AutoCAD 2010 then you must have a standalone version of AutoCAD raster design 2010. So you have a Standalone version of AutoCAD 2010 and a Network version of AutoCAD Raster Design 2010 then they will not install together.
From the AutoCAD Raster design readme file:
Install and License Methods Must Match Host Application
With the new license system, AutoCAD Raster Design installation and licensing methods must match that of the host AutoCAD-based product. For example, if you install the host application as a network installation, you must also install AutoCAD Raster Design as a network installation.