On the one hand, taking code from your employer and posting it to GitHub with the copyright notices removed is about as clear-cut a case of copyright infringement as you can get -- if they have evidence. Should be easy to confirm or deny by looking at version control history.

(This seems to be the repository in question, but it's been taken down: https://web.archive.org/web/20210104032001/https://github.co...)

On the other hand, the patent claims referenced in the lawsuit seem to me like great examples of software patents that ought to be struck down for being uselessly over-broad. For example, I would love to hear an argument as to how the "'433 Patent" wouldn't be infringed by running Wireshark in a Kubernetes pod. That meets every single one of the claimed elements that Splunk is claiming Cribl is infringing.