Yes, all of these resources are in English, as it is the target language for the classroom. The expectation is that the teacher's language proficiency should surpass that of their students regardless of grade level. While anyone can download the files, these resources are primarily intended for language teachers to use in their instruction.
There's no catch. All resources here are free. The material is a collaborative effort between teachers who want to make English classes interesting and fun. The videos are short which means they can be watched and then used for an activity that can be finished in one class. This is differs from using videos as a filler or passive activity.
EN-US 
JA-JP