Hello Vladimir,
1. In this thread https://discuss.kotlinlang.org/t/postgresql-support-in-exposed/406 Ilya says that you use it internally - this is very interesting. Does you still use it(a year has passed since last thread post)? Are you satisfied or not? Is this project under heavy load or not?
Indeed, https://account.jetbrains.com plus e-commerce, sales support, CRM, a license server that IDEs connect to, all are 100% Kotlin on Exposed + Kara. Maximum load we had thus far is 7K requests per minute, growing significantly after the subscription switch. Everything scales pretty well.
2. By github commit history I see that project is under development, but what is worrying me is that even after two years there is still no any releases, no any build system is used. It looks more like a pet-project. So question is - is there serious project for committers or just experiment? What future plans do you have on this project?
Indeed, we use it, we like it, we make it better when we find shortcomings based on our practical usage, but haven't found time yet to spend dedicated resources on the project itself. It lacks a build, distribution, documentation and we only sure it works for MySQL, which we use in production and a H2, which we use in unit tests.
3. There is one old pull-request from apatrida user, it contains gradle integration & another changes. Pull is not integrated nor commented about problems(if was any). Are you acceptin pull-requests?
Well, what we do internally is we include Exposed sources directly into the larger project setup, that's why we just don't need a build. The other changes include different query DSL which, if accepted, will not work with our larger project. Thus we just can't accept it regardless if it's for bad or better.
Hope it helps,
Max