You can find its ancient source code from 1999 here: https://github.com/ssg/sozluk-cgi
The platform is currently at https://eksisozluk1999.com because its canonincal domain (https://eksisozluk.com) got banned. Any visitors from outside Turkey should get redirected anyway.
Since it's still a legal business entity in Turkey, it keeps paying taxes to Turkish government, and even honors content removal requests despite being banned. Its appeals for the bans are in the hands of The Consitutional Court to be reviewed for almost a year now.
A newspiece from when it was banned the first time this year: https://www.theguardian.com/world/2023/mar/01/eksi-sozluk-wh...
Its Wikipedia page: https://en.wikipedia.org/wiki/Ek%C5%9Fi_S%C3%B6zl%C3%BCk