Thanks @marcos, maryo's compiled version worked for me.
For the record, I dropped this DLL into
C:\Bitnami\dreamfactory-1.9.4-1\php\ext\ replacing the included DLL, restarted Apache, and immediately the module enabled okay:
C:\Bitnami\dreamfactory-1.9.4-1\php>php.exe -m | findstr ibm
I also tested this driver with an actual IBM DB2 connection through the DreamFactory application, and it worked.
Looking forward to seeing the correct DLLs included in the Windows Bitnami packages.