There doesn't seem to be any mention until you try to find the app that everything related to CacheBox seems to be in German.
Cachebox is a german project but you can switch the app´s language to english, no prob.
That´s right, but as you already found out, you can download it at sourceforge.
This is necessary to call a "telephone joker" directly from the app, although this is not implemented yet.
Don´t worry, just give it a try.
If there are any questions left, feel free to ask in the related forum, it´s german speaking, but most of us speak english as well.
CU
Toette (No developer, just a happy user)