<neckbeard> IIRC, the Apache project started around the Apache http server, written in C. Apache http server 1.0 was released ~7 months after Java 1.0. </neckbeard>

Apache TVM [1], which is a tensor compiler stack focussed on deep neural networks.

It is mostly written in C++ and Python, integrates external libraries like LLVM, OpenCL, CUDA, etc.

[1] https://tvm.apache.org/

Airflow is probably most known one, also built on python

Apache Arrow is another one (analytics memory format), it supports a whole litany of languges via C++ bindings, too many to list.