Downloads of stable releases are available here. It is recommended that you use the latest stable release for projects.
Latest releases:
Download latest stable version (4.5.3, for OMNeT++ 6.x) (What’s New)
To help porting old INET based models to the latest OMNeT++ version, we provide an OMNeT++ 5.4 compatible version of some popular versions of INET. These versions can be used as a starting point for the porting work.
Installation instructions are available here.