Are they on the GOG version?

Sadly, they are not present.

Titles are present. Basically, getting the last title equals getting all achievements.

Ah so they're just in game?

Agarest have in-game system "Titles". You get them for killing XX monsters, getting XX items, etc., almost like achievements, and you get actual in-game rewards for completing them. Last Title basically says - complete everything possible, get all items, spells, etc. But Steam and consoles have their own achievements, which have nothing to do with the titles and don't give any actual rewards.

To be honest they are not exactly achievements per se - more like challanges, completing them with rewards you with stuff. And generally you will have to use it.
Still, to be fair, some achievements are linked to those titles, so...

One of the best achievements of systems that I've seen in games.