I've created my own DSL, and instruct Claude Code how to generate code for this DSL using skills.
Since this is a new language, and not documented on the web nor on Github, Claude's ability is not based off of stolen IP. At best it's trained on other language concepts, just like we can train ourselves on code on GitHub.
Maybe a good reason to create a new programming language?
Interesting, but I still do not think this is as easy. The AI model is still trained on some existing works, and it is generating code in the new DSL or programming language still based some higher level ideas and expressions it has consumed during training. You have added just one more level of indirection. The output cannot anymore be verbatim copy of some existing work or non-short snippets, however, the output may still carry "expression" that are substantially similar to something pre-existing.
Note: IANAL. The above is just from my current understanding.