Here are their terms and conditions:
You give me money, I’ll give you creative. I’ll start when the check clears. Time is money. More time is more money. I’ll listen to you. You listen to me. You tell me what you want, I’ll tell you what you need. You want me to be on time, I want you to be on time. What you use is yours, what you don’t is mine. I can’t give you stuff I don’t own. I’ll try not to be an ass, you should do the same. If you want something that’s been done before, use that.
PRO BONO If you want your way, you have to pay. If you don’t pay, I have final say.
Let’s create something great together."
In case you're wondering about the legality of this, Basecamp's Founder and CEO Jason Fried remarks:
For those who will be quick to point out legal holes or missing protections, there are many ways to do business. One way is working with clients you trust — people who appreciate this approach to work. And if you guessed wrong, and someone fucks you, rather than pursuing legal remedies which cost even more time, money, and hassle, there’s an alternative: Take your losses, wash your hands, and don’t work with them again.