[MENTION=584410]mozilla[/MENTION], popular to roll out the CoC here, but it doesn't apply. The Contract of Carriage applies to tickets and the actual transport of passengers. From United's site ( bolding mine ):

Transportation of Passengers and Baggage on flights operated by United Airlines, Inc. ("United"), Carriers doing business as United Express, and other carriers operating as United's Codeshare partner (collectively "United Carriers"), are subject to the terms and conditions set forth in United's Contract of Carriage, in addition to any terms and conditions printed on or in any ticket, ticket jacket or eticket receipt. By purchasing a ticket or accepting transportation, the passenger agrees to be bound thereby.

CoC doesn't apply to every interaction with United -- for example if you purchased a UA gift card or a stuffed Polaris bear, you're not bound by the CoC. That's governed by general commercial terms, and any specific terms of the channel you use. For United.com, you'll find those terms here: https://www.united.com/web/en-US/content/legal.aspx

They make that even more clear at the bottom of that page (again, bolding mine):

Transportation of passengers, baggage and cargo by United and certain regional carriers d/b/a United Express® is subject to the terms and conditions contained in United’s Contract of Carriage, in addition to any terms and conditions specified on united.com, printed on or in a ticket jacket, ticket receipt, or in any published schedule. By purchasing a ticket and accepting transportation, the passenger agrees to be bound by such terms and conditions. Other services and products described in this website will also be subject to terms and conditions, details of which may be obtained from United Airlines or its service provider (as applicable).

FareLock, as you noted above, is not purchasing a ticket, so you'd fall into the 'Other services and products described in this website'... category.

It's nuanced, but UA is in the wrong here. They shouldn't be cancelling duplicate FareLock reservations, and definitely shouldn't be keeping the money if they do. As a practical matter though, I'd bet this is an IT issue. There's code in their system that looks out for CoC 5H, cancelling duplicate reservations in general, and it probably doesn't discriminate between FareLock and non-FareLock reservations. I strongly suspect anybody who brought a lawsuit would win it and force change here, but the dollar amounts are so small it's probably not worth it.