Yes, you can use MonkeyLearn in other languages when you create a custom module. You will have an opportunity to define the language during the process of creating one, or after in the "Parameters" tab.
For our public modules in MonkeyLearn, we specify in which language these modules are offered in the title of the module. Public modules need to be specialists on a language and task, so they can't be used for other language sets. At this point, most of them are limited to either English or Spanish.