I placed an order on half.com without the coupon(s) and received an email:

Take Five!
Send your friends a $5 coupon. When your friends make their first purchase on half.com you'll receive $5! Take $5 Now!

When I clicked the link I've got a referral page with the following Terms and Conditions (see below). So if you want to buy something for $10.00 or more at half.com, and you haven't bought from them before, and if you want a $5 discount, please PM me your first name and email address (to fill out the form) and I'll send you a referral. Apparently the coupon code will be generated when the referral is sent.

Take Five! - TERMS AND CONDITIONS
By participating in the Take Five! Program (the "Program"), you acknowledge that you have read, understood, and agree to be bound by these Terms and Conditions.
1. ELIGIBILITY. This Program is open only to US registered users of half.com and on the following terms and conditions. No purchase is necessary to participate in the Program.
2. PERSONS WHO MAY BE REFERRED. You must only refer individuals to half.com who you have a personal or business relationship with and who you believe would like to receive a coupon from half.com (a "Friend").
Without limiting the generality of the foregoing, you must not submit for referral: i) group e-mail addresses, ii) e-mail mailing lists, or iii) yourself.
3. NUMBER OF REFERRALS. There is no limit to how many friends you can refer through the Take 5 Program. However, you may refer each friend only once.
4. COUPONS SENT TO FRIENDS. half.com will, if it determines in its sole discretion that you have complied with these Terms and Conditions, send on your behalf an e-mail to each Friend that you refer to half.com before the Program closing date which half.com may determine from time to time in its sole discretion, so long as that Friend has (a) not already previously purchased products from half.com, (b) not already been referred to half.com by another party; and/or (c) opted to receive e-mails from half.com. Each e-mail that is sent under this Program will contain a code good for $5.00 dollars off of a $10.00 dollar purchase (or such other amount that half.com determines in its sole discretion from time to time).
5. COUPONS SENT TO YOU. For each of your Friends that qualify for and are sent a coupon code under this Program and become a new customer of half.com, half.com will send to you a coupon code good for $5.00 dollars off of a $10.00 dollar purchase with an expiration date set to be 7 DAYS from the day of the Friends purchase (or such other amount that half.com determines in its sole discretion from time to time). A Friend will only be deemed to have become a new customer for the purposes of these Terms and Conditions at the time that he or she places an order with half.com. half.com will not send a coupon code to you unless and until it receives an order from that Friend.
6. REMEDIES FOR YOUR NONCOMPLIANCE. If half.com determines in its sole discretion that you have not complied with these Terms and Conditions, it may, in addition to any other rights and remedies it may have against you, immediately and without notice to you, withdraw all benefits to you and your Friends under this Program, including, without limitation, by canceling or declining to send any and all coupon codes issued or to be issued to you in connection with this Program and, by declining to send or stopping from being sent, any Take Five! e-mails.
7. YOUR CONSENT TO USE YOUR DATA IN EMAILS. You grant to half.com your consent for it to use your name and e-mail address for the purposes of sending an e-mail to your Friends in the form displayed on the e-mail preview page (see the Take Five! Welcome Page). You agree not to use any false e-mail addresses or names for this program.
8. YOUR REPRESENTATIONS AND WARRANTIES TO US. You represent and warrant to half.com that you have an existing business or personal relationship with each Friend and that it is your genuine opinion that each Friend would wish to receive a coupon code from half.com. By providing us with the names and email addresses of your Friends, you are affirmatively requesting and authorizing half.com to send them an email, as outlined herein, on your behalf.
9. COUPON TERMS AND CONDITIONS. Each coupon code issued to Friends under this Program will expire within 7 days of the date that the e-mail containing the coupon is sent to that Friend, or on the earliest date permitted under applicable law, whichever occurs later.
10. LIMITATION OF LIABILITY FOR half.com. TO THE FULLEST EXTENT PERMITTED AT LAW, NEITHER half.com NOR ANY OF ITS AFFILIATES, DIRECTORS, EMPLOYEES, OR OTHER REPRESENTATIVES WILL BE LIABLE FOR DAMAGES ARISING OUT OF OR IN CONNECTION WITH THIS PROGRAM. THIS IS A COMPREHENSIVE LIMITATION OF LIABILITY THAT APPLIES TO ALL DAMAGES OF ANY KIND, INCLUDING (WITHOUT LIMITATION) COMPENSATORY, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES; LOSS OF DATA, INCOME, OR PROFIT;
LOSS OF OR DAMAGE TO PROPERTY; AND CLAIMS OF THIRD PARTIES.
11. ENTIRE AGREEMENT. These Terms and Conditions represent the entire agreement between you and half.com with respect to the Program.
12. VARIATION OF THE TERMS AND CONDITIONS. These Terms and Conditions may be amended or modified by half.com in its sole discretion at any time. Any such amendments will be posted to this page, and it is your responsibility to review this page from time to time for such amendments.
13. CURRENCY AND TIMES. All amounts stated in these Terms and Conditions are in U.S. dollars, and times and dates are based on Eastern Standard Time.
14. SEVERANCE. If any provision of these Terms and Conditions is held to be invalid, such invalidity will not affect the remaining provisions.
15. GOVERNING LAW. These Terms and Conditions will be interpreted, construed, and enforced in all respects in accordance with the laws of the State of Pennsylvania, without giving effect to any principles of conflicts of laws. You hereby irrevocably consent and submit to the nonexclusive personal jurisdiction of the state and federal courts within Montgomery County, Pennsylvania for the purposes of litigating any such action.