eTicket is based on osTicket. They both have different developers.
Read the FAQ section on the eTicket site.
Why does eTicket exist? / What happened to osTicket?
-- Until late 2007, there was no official release of osTicket since 2005, during this time many bugs, problems and issues have been idenified, yet nothing was officially released to resolve them.
-- In addition to this the official download of osTicket was removed.
-- In 2005 it was said that osTicket 2.0 was in the pipeline, however this never appeared, also as this was going to be a complete rewrite, it was suggested that you would be unable to upgrade from previous versions of osTicket to osTicket 2.0, therefore leaving a gap for support.
What is the difference between osTicket and eTicket?
-- The purpose of the eTicket project is to take the last official osTicket release and resolve all known problems and add requested features.
-- Almost every single piece of code has been changed, however the basic structure remains the same to make it easy for users to upgrade from the old osTicket to the new eTicket.
-- It was released under the eTicket name so people are aware of the change in development.