1) What is the exact definition of a kuti chaver? Is he permitted to observe more mitzvoth than just the 7 of Bne Noach?
2) What about a non Jew?
3) Do Chazal ever mention kehillot of non-jews who kept. more than the 7 mitzvoth shel Bne Noach Any sources?
Lopes Cardozo , Israel
1&2. A Kusi Chaver is no more or less a Jew than any other Kuti, and as such no more or less obligated to keep Mitzvos. There is a Machlokes as to whether Kusim are considered to be Jews or not (Kidushin 75b). According to the opinions that a Kusi is a Jew he is obligated in the same way as any other Jew. According to the opinions that a Kusi is not a Jew, he is like any other non-Jew.
The Rambam (Hilchos Melachim 10:9-10) as explained by the Radvaz, says that a non-Jew may only keep Mitzvos on the understanding that he is not obligated to do so but is doing the Mitzvos voluntarily. This ruling is based on the Gemara in Sanhedrin (59a).
3. I am not aware of any instance of Chazal discussing groups of non-Jews keeping Mitzvos without becoming Jews, besides for the Kusim.
Dov Freedman