I'm building one! It's still under heavy development. Doing a lot of yak-shaving trying to get the internal architecture to suck as little as possible. Jenkins is surprisingly complex. Things that seem like should be simple, turns out is difficult to implement in a way that isn't horrible, when everything is a plugin. The good news is, at the pace i'm going, it should be production-ready in about 2 years :D But at least it will be GPL, and not strangled by some company trying to monetize it.
If you want something today that's closest to Jenkins in design, that would be StackStorm. It's not very trendy, but it has basically everything you need, and a flexible, pluggable architecture. They open-sourced all the Enterprise components too.
Not sure what you mean by "strangled", Jenkins seems quite to open to me, in fact I'm paid to take care of its OSS infrastructure and its community and only that, by the main company behind it, and they don't ask anything more, I feel quite free in my job.
If you want something today that's closest to Jenkins in design, that would be StackStorm. It's not very trendy, but it has basically everything you need, and a flexible, pluggable architecture. They open-sourced all the Enterprise components too.