Sorry I am late getting into this thread ...
You may want to check out the Oracle Instant Client. This has a substantially smaller footprint than the normal Client software and is easy to install - just put the package of files on the server that you want to connect to Oracle and use the proper connect string.
You do not need to worry about O/S as this approach is basically universal.
One other Client you may want to take a look at is the JDBC connector. This is VERY small (about 20K) and is quite portable. The approach is similar to ODBC, but more secure and easier to use.
Sometimes you are the windshield
Sometimes you are the bug