I'm currently knee-deep in trying to find out if there exists a Redbrick DB client/ODBC-hoohaw for Linux. This is all complicated by the fact that while some people claim that Redbrick == Informix compatibility, others say Redbrick != Informix compat.
The Python InformixDB client hasn't been updated this millenium, which either means it's perfect or dead.
Willing to pay $$$ for Redbrick connectivity, contact redbrick@gurno.com!