This is a gray area. You legally own Anno 1404 Venice. The eng0.rda is not a crack or a pirate executable—it is a proprietary data file. Ubisoft does not officially redistribute single language packs for the classic version.
Find the line that says ger (or whatever language is currently set). Change it to: eng. Save and close the file. Troubleshooting Common Issues Anno 1404- Venice ENG Language Pack -eng0.rda-