The feature you have described is called “home page redirection.” There are issues. Nomadix holds a patent which they claim covers all home page redirection at wireless hotspots, whether the service is free or paid. You can read about it here:
The Orinoco AP-2500 supported this feature back in 2002. I don’t know the current status of this product.
Cisco provides home page redirection under another name as part of the AAA process in conjunction with a RADIUS server, but that’s not a cheap solution.
If you find something, either Linux or Windows, please let me know about it. –Bob Young