I'm afraid one of my clients might ask his fellow software engineer to design a few page templates for a WordPress-based community I'm redesigning, according to my code and design. He just bounced me back an estimate cutting down expenses on page templates and leaving only the frontpage template, which is clearly the only one he can easily replicate into multiple page templates, for the core pages whose templates he just dismissed.
Is there any way to protect my code and designs with strict licensing? Are there any ways to protect my work from being copied by my own client? Which licenses should I use?