It came up here: Score Estimate vs Result - #11 by gennan
Also, someone mentioned seki detection was implemented in GnuGo, which is open source: Score Estimate vs Result - #22 by SouthernGoPlayer
I don’t know if anyone is working on porting it to OGS, but I assume nobody is.
I did consider to try it myself, but I’m sort of always lacking time. And if I would, I’d pick my favourite programming language for it, which isn’t PHP or javascript.