Binder is "weird", Kroah-Hartman said. It came from BeOS and its developers were from academia. It was developed and used on systems without the System V IPC APIs available and, via Palm and Danger, came to Android. It is "kind of like D-Bus", and some (including him) would argue that Android should have used D-Bus, but it didn't. It has a large user-space library that must be used to perform IPC with binder.
Binder has a number of serious security issues when used outside of an Android environment, he said, so he stressed that it should never be used by other Linux-based systems.