From their blog:
http://community.namecheap.com/blog/2013/04/19/earth-day-2013/
For every domain name transferred to Namecheap on Monday, April 22nd, you will not only save big (transfers are $5.99* for com/net/org/biz/info) but we will also be donating $1 on your behalf to the organization of your choice based on the coupon code you will use.
That’s right, we have two coupon codes. **DONATE2WWF **is the coupon to use if you want to donate to WWF. **SAVETHEFOREST **will support the Rainforest Alliance.
Conditions:
An additional $0.18 ICANN fee is charged to .com and .net transfers.
Limit 10 domains per household or business entity across both coupons. Limit 1 hosting plan per household or business entity across both coupons.
Domains transferred out of Namecheap previously are ineligible to participate in this promotion.