I run a free website that lets users pull data out of a database that I maintain. Sometimes users make suggestions as to improvements to existing reports or new reports they would like to see. While most are good suggestions, I don't always have time to implement them (I maintain the site in my free time).
I would like to put on GitHub the Perl/MySQL code that generates everything that the users see to allow those that want to make improvements on their own to do so and I can simply push them into production. I'll probably post a small sample database that they can use to confirm their contributions work.
If they want to use any portion of my code in other projects, I'm fine with that. If they want to download my entire database and modify my code on their personal web server so they can get the exact reports they want, I'm fine with that. If they want to download my entire database and create their own public front-end for it based on my code, I'm fine with that.
The only thing that really worries me is someone downloading my entire database and code, modifying the code to harm users in some way, and then publishing it on their own webserver(s) with domain name(s) close to mine and pretending to be my site. There are already sites with domain names close to mine targeting my users
How do I maintain enough copyright in my code to take down any copycat sites while putting it on GitHub for anyone to use in any other way?