My prefered language in Oracle Data Modeler is English.
If the language is not English here are the steps to change this:
Add the line following line to the file datamodeler.conf in the directory datamodeler\bin\. On a Mac it is in the OracleDataModeler-VersionNumer.app in the folder Contents\Resources\datamodeler\datamodeler\bin\
Restart Oracle Data Modeler.
Got the tip on the webpage:
Memosoup.com – change interface language