http://www.milknhoney.co.il/torah/yitro3.htmlYitro - Converting to Judaism
In our Perasha Moshe Rabienu's father in-law, Yitro, comes to visit Moshe. Yitro previously was a priest from Midyan. He came when Benie Yisrael were still at the foot of Mount Sinai. He had heard about everything that G-d did for Benie Yisrael. According to certain Midrashim, when he heard what had happened he converted to Judaism.
With regards to Avraham Avinu it is said that whoever brings a gentile close to G-d it is considered he created that person.
During the time of the Second Beit Hamikdash many felt that the Laws in the Torah were Universal. Therefore, many actually missionized. Others who did not missionize still were very accepting of all those who wanted to convert.
There are famous stories about insincere converts who were converted by the famous Tana Hillel. Each one came to him after being turned away by Shamai. One wanted to be converted on condition that he only need to follow biblical Torah but not Rabbinic. Another wanted to be converted if he could learn the torah on one foot. Still another was into the fine clothing worn by the Cohen Gadol. He wanted to be converted only if he could become Cohen Gadol.
After some time passed all of these converts met each other. By this time they had overcome their eccentricities and were dedicated, observant Jews. They praised Hillel for accepting them with their problems.
Akilas the convert was Hadrian the Wicked's nephew. When Akilas wanted to convert he told Hadrian, who responded by saying that he had oppressed and killed many Jews. Akilas told him that even the smallest children know how G-d created the world.
This movement of Tanaim clearly beleived that Torah is good for all of Humanity. If it is good for all of humanity then certainly we should not keep it to ourselves.