Free WordPress Installations

Just so we understand what you are offering. You want to allow people to install WordPress, for free, on your domain as a subdomain? And what would they contribute to a “free” WordPress hosted site? Or are you looking for a place to get free hosting with a WordPress site?

You might want to chat to the folks who hang out on the WordPress MU forums. Some of them should have some insights into this:

https://mu.www.ads-software.com/forums/

Most “free WordPress” sites, like Blogsome and WordPress Blogs, are done by using WordPress MU. However, there are a few other ways to accomplish this. They are all listed in detail here: https://codex.www.ads-software.com/Installing_Multiple_Blogs