The libaries are meant to unwind the application and storage layers, making applications and code using these libraries independent of the underlying Exchange or Outlook version. It also enables certain applications/scripts to run remotely (mostly apps/scripts from the pre-PowerShell era). Only problem you can encounter is when applications/scripts make use of certain functionality only to be found in certain Exchange/Outlook versions, requiring specific MAPI or CDO library versions.
These libraries may be required by certain 3rd party applications, scripts, etc. that need to interface with Exchange, e.g. Blackberry Enterprise Server, the Transporter Suite (for Notes-Exchange co-existence/interoperability), Quest Exchange tools, etc. etc.
Note that MapiCDO release follows Exchange Server 2003’s lifecycle and it is recommended you upgrade your application or port your application/script to and start leveraging new Exchange interfaces, e.g. Exchange Web Services, Outlook Object Model or the Outlook MAPI Client Library.
ExchangeMapiCDO 1.2.1 version 6.5.8165.0 can be download here.