To name a few (each have data that can be downloaded):

- Jibiki.fr (Japanese-French)

- CFDict (Chinese-French) https://chine.in/mandarin/dictionnaire/CFDICT/

- 教育部臺灣閩南語常用詞辭典 (Taiwanese Hokkien) https://twblg.dict.edu.tw/holodict_new/ https://github.com/g0v/moedict-data-twblg

- 台日大辭典 (Taiwanese Hokkien-Japanese) https://github.com/fhl-net/Lim-Chun-iok_2008_Tai-jip-Tua-su-...

- Littré XML (French) https://www.littre.org/faq

- 重編國語辭典修訂本 (Chinese)

Note that all have different, sometimes incompatible license. In particular dictionaries from Taiwan's Ministry of Education usually don't allow derivatives.

There is also a lot of dictionaries digitized on Archive.org that felt into public domain would require transformation into text (actually the Jibiki project did that with the Cesselin).

Well Wordnet is often described as a combination of a dictionary and thesaurus structured so a computer can understand it https://wordnet.princeton.edu/

In my experience Wordnet as an English dictionary is much worse than the dictionary (the New Oxford American Dictionary) included with Macos and iOS.

I run a russian-english/russian-german Open Data dictionary, https://openrussian.org

I'm sure you know it, but there is https://www.wiktionary.org/ too

My dad's German Persian dictionary is freely available on https://farhang.im with source code on https://git.hmt.im/hmt/farhang-3 I haven't yet found the ideal way to share the sqlite database file in a current state.

One of the older and well-known ones is Jim Breen's WWWJDIC (Japanese–English):

http://nihongo.monash.edu/cgi-bin/wwwjdic

(Creative Commons Attribution-ShareAlike Licence)

The dictionary files are used in a lot of websites and apps that provide a Japanese–English dictionary.

CC-Canto[1] is an open source Cantonese-English dictionary.

[1] - https://cantonese.org/about.html