Yeah, LocalStack seems to be a similar idea, with more support for the "new stack" (e.g. lambdas) and a bigger focus on testing/mocking AWS during dev rather than replacing AWS for production workloads.

In contrast Eucalyptus was more for run-your-own-AWS in your data centre. See https://en.wikipedia.org/wiki/Eucalyptus_(software) and active code branch here https://github.com/sjones4/eucalyptus