The SNMP/eCos package consists of two eCos packages; the SNMP library and the SNMP agent.
The sources are arranged this way partly for consistency with the original release from UCD, and so as to accommodate possible future use of the SNMP library without having an agent present. That could be used to build an eCos-based SNMP client application.
The library contains support code for talking SNMP over the net - the SNMP protocol itself - and a MIB file parser (ASN-1) which is not used in the agent case.
The agent contains the application specific handler files to get information about the system into the SNMP world, together with the SNMP agent thread (snmpd in UNIX terms).