UltraEdit appears in the language defined as system language as written on UltraEdit for Mac/Linux download
page (Mac OS standard). So one method to work with UltraEdit in French is changing system language
Another method is downloading and installing Language Switcher for Mac
which is a tool giving the Mac user the opportunity the choose for each application one of the languages supported by the application different to system language.Note:
I don't have a Mac and therefore don't use UltraEdit for Mac. I posted here only information found by me quickly in world wide web by searching for Mac application specific language
with a search engine.