Sorry for not including this important detail on the main jam page! Yes, I had planned for it to be only English. This is mostly because I don't have the skills to determine which games to include otherwise.
However, there is a bit of flexibility in that last part. If there is a game that (for some reason) can be engaged with and enjoyed by someone who doesn't speak the language, then it would certainly be welcome in the jam. It's hard to imagine what that could be, but maybe something that is very simple and primarily visual (which could be fun for the player to translate) or where the language divide is part of the game (such as Spanish on one side, and English on the other).
All this is to say that the audience is considered primarily English-speaking, so if you have a game they can enjoy, it's certainly welcome in the jam.
If the series continues in the future I would love to branch into different languages - but this will require some collaboration as I don't have those skills myself.