Terachess was designed in 2008 and appeared soon after on Jocly. But it was in April 2020 that I have made more major changes and in order to keep a trace of the first version, I made a new page called Terachess II. So you are right.
In case it is useful, Gigachess had a similar evolution except that it was first designed in 2001. Gigachess II was completed in April 2020 too.
Terachess was designed in 2008 and appeared soon after on Jocly. But it was in April 2020 that I have made more major changes and in order to keep a trace of the first version, I made a new page called Terachess II. So you are right.
In case it is useful, Gigachess had a similar evolution except that it was first designed in 2001. Gigachess II was completed in April 2020 too.