Apex is a framework used to help build and deploy applications on Lambda. This project appears to be a way to run your own Lambda service locally. There are other projects out there like OpenWhisk[1], Iron Worker[2], Gestalt[3], and Funktion[4].

[1] - https://github.com/openwhisk/openwhisk

[2] - https://www.iron.io/platform/ironworker/

[3] - https://galacticfog.github.io/

[4] - https://github.com/fabric8io/funktion

(Edited for Formatting)