The intent was to allow the DLLs to be freely distributable with applications developed using the API.
Distributing the full API as part of installs might distribute a less recent version than the one avaliable
from Esri (which is a similar situation to why individual users must download the Java JDK, and not
have it distributed elsewhere). What particular language has you concerned?
The current code is in beta, and subject to the Beta Agreement (no early distribution).
-V