1) Chizkuni: Chezekiah ben Manoach, 13th Century, France
It doesn't mean to love your neighbor as yourself, because it is impossible to do that, rather the meaning of love is: to be good to them just as you would like that they would do to you.
2) Rambam: Moshe ben Maimon, Spain 1134-Egypt 1204
It is a commandment to all people to love each and every Jewish person as themselves, as it is written: "Love your neighbor as yourself" therefore people should say good things about others, and to be careful about others' money just as they would be careful about their own money, and desire honor for themselves.
3) Talmud: Tractate Shabbat 31a
It happened that a non-Jewish person came to [the head Rabbi] Shammai and said to him: "Take me as a convert, on condition that you teach me the entire Torah, all of it, while I stand on one foot." Shammai instantly drove him away with a builder's measuring rod...When the non-Jewish person came to [the other head Rabbi] Hillel, Hillel agreed to make him a convert, saying: "What you don't like, don't do to your neighbor--this is the entire Torah, all of it, the rest it commentary. Go and study.
4) Kli Yakkar: Shlomo Efraim Luntschitz, Poland (1550-1619)
Certainly, in the case of the convert he asked [not to say all the mitzvot while standing on one foot, rather to] stand all the mitzvot in the Torah on one founding principle...so that they [the mitzvot] wouldn't be forgotten. In response, Hillel taught him "Love your neighbor as yourself."