How is Mojarra different from Sun's JSF Reference Implemenation?
Is it just a later version? Is it simply a rename?
The Sun JSF Reference Implementation, also known as Sun JSF RI, was named like that, just "JSF RI", from the beginning on until version 1.2_08. The dev team found it an extremely boring and nothing-saying name. They would like to participate with the fancy product code name hype and wanted to have it in line with the "Glassfish" project which JSF RI is part of. After some user community polls (initiated by the good ol' forums.sun.com), the name "Mojarra" was been chosen. Since version 1.2_08, the name "JSF RI" has been replaced by "Mojarra". But it's essentially the same implementation. In other words, Mojarra is the JSF Reference Implementation.
Later, when Sun was taken over by Oracle in January 2010, the company name "Sun" was obviously replaced by "Oracle". And yet later, when Java EE was reowned by Eclipse instead of Oracle in September 2017, the "Java EE" project name was renamed to "Jakarta EE" (for legal reasons because Oracle owned "Java" trademark) and the company name "Oracle" throughout JEE was replaced by "Eclipse".