Actually, a DB2 Connect installation (not free) is only required for access to DB2 on iSeries or zSeries machines from Linux, UNIX, or Windows.

To access DB2 on Linux, UNIX, or Windows, you just need to download a free DB2 client (Runtime, Administration, or Application Development) from DB2 Support.

If you're compiling DBD::DB2, get the DB2 Application Development Client and ensure you select the "Install Headers" option.