Here is the information you're looking for on contributing to translations: About Translating App Inventor
We have prototype code for right-to-left languages that we have never used because a right-to-left language has never been completed to the point where we can test against it. We would be very excited to see volunteers work on this.
The second link is the important one, and what's not clear here is that this is two out of three modules. The largest module is OdeMessages, which contains the text for the designer GUI and all components. This module hasn't been translated. Note that OdeMessages is huge, and all of it does not need to be complete for a translation to be released and useful.
I'm going ahead and creating a file for OdeMessages in Hebrew to make this clearer.