This project uses the English-Czech dictionary from https://www.svobodneslovniky.cz to create a Czech-English dictionary and to add inflections to every word. You probably don't need to run this, but if you do, you first need to create the lemma database using this.
The finished dictionaries are available here in Tabfile and Stardict format. Their license is GNU/FDL/CC-BY-SA-NonCommercial
The inflections come from https://ufal.mff.cuni.cz/morfflex.