What are the implications of "Ba'er Heitev"?
Rashi (citing Sotah 32b) and Targum Yonasan #1: It implies in (all) seventy languages 1 (but in Lashon ha'Kodesh script, exclusively - Targum Yonasan). 2
Ramban and Targum Yonason #2: It means that they were written in a clear script.
See Ba'al ha'Turim. Moshav Zekenim: So that, in the event that a gentile will pass, he will recognize his language and understand, and take to heart to fulfill the Mitzvah. Refer to 27:8:22:1*.
See Na'ar Yonasan, who elaborates.
Why did they need to write the Torah in seventy languages?
Oznayim la'Torah (citing a Midrash): Hakadoh-Baruch-Hu put into the minds of the nations to copy the Torah in their respective language; so every nation sent a notary to copy it. 1
Oznayim la'Torah: This was in answer to the nations of the world who accused Yisrael of stealing Eretz Yisrael from the Cana'anim So they would now see, black on white, that Hashem created the world, and that He was therefore authorised to give it to whoever He pleased - first to Cana'an and then to Yisrael. See opening Rashi in the Torah, and Oznayim la'Torah, who elaborates.
Why did they need to write the Torah on the stones?
Rashbam: So that, when Yisrael swore on Har Gerizim and Har Eival, the whole Torah was written in front of them and they swore that they would keep it.
