I'm sorry, but shit like this completely ruins the design industry. You shouldn't let people get used to getting stuff for free, especially not if it's an important profession that should be paid for. If you want to practice, fine. But don't do it at the cost of others. Garages don't fix your car for free because they need to practice.

If you want design practice the best idea would be to just go on craigslist and do someones website for around ~$500 dollars. Or even better yet do your own website.

Honest question but if your goal is to get some practice, why does it matter if it's a running startup or not?

One thought: projects "already in-progress with a real product or service" may have more of a need for incremental tuning than a "complete redesign".