Jews do not convert to Karaite Judaism or for that matter any other form of Judaism. Once you become knowledgeable as to the practices of a particular form of Judaism and agree with its principles of faith you become a member of that branch. It is no different with Karaite Judaism and our Introduction modules are designed to teach those principles which are the fundamentals of our faith.
Joshua son of Nun was our prophet, leader and scribe who stood by Moses’ side at Sinai and with Moses later lead the Children of Israel through 40 years of wanderings in the desert. Surely if anyone, other than Moses, knew whether God gave an Oral Torah to Moses at Sinai, it would have been Joshua, upon whom the Torah says YHWH placed his spirit. Yet the words in the Book of Joshua refute the notion of a separately transmitted Oral law to Moses by stating:
And afterward he [Joshua] read all the words of the law, the blessing and the curse, according to all that is written in the book of the law. There was not a word of all that Moses commanded, which Joshua read not before all the assembly of Israel, and the women, and the little ones, and the strangers that walked among them.
Joshua read the law of Moses to the Israelites to acquaint the Jewish people with the laws of the Torah and to teach them to carry out the covenants, statutes, ordinances and commandments that YHWH had given to the Children of Israel. Yet, our Rabbinic brethren claim that an oral torah was simultaneously transmitted to Moses. The Book of Joshua, however, which goes into great detail about Joshua's reading of the law to the Israelites, fails to give the slightest hint as to how Joshua could have read the 'oral law'. Karaites believe that significantly after God gave the written Torah to Moses, the "oral" or supplementary laws were developed by those who failed to search the Scripture for its proper meaning. Karaites believe that an honest and thorough search of the Hebrew Bible answers most of the questions which the Talmud seeks to address. This belief distinguishes and separates Karaism from the rest of today’s Jewish movements. We seek to educate our fellow Jews, so that all of Israel may return to the Judaism of the Bible.