I have added ODBC support to the sqlserver adapter by way of an optional :mode parameter. If :mode is set to ODBC, an additional :dsn parameter is tested for and used in conjunction with :username and :password to establish a connection using DBI:ODBC. I'm attaching a diff to patch in this functionality as well as a connection.rb example for test/connections/native_sqlserver_odbc/.
If :mode is omitted, ADO is assumed and the adapter functions as it did previously.
Both the ADO and ODBC modes pass all the base tests. The ODBC mode fails the same tests in the full suite that the ADO version already failed.