Most companies have TOS that include not damaging or attacking the company itself. The advertised service attacks Cloudflare explicitly. It seems very straightforward that this would violate any reasonable TOS.
edit: and here it is straight from their TOS
https://www.cloudflare.com/en-ca/website-terms/
"7. PROHIBITED USES
As a condition of your use of the Websites and Online Services, you will not use the Websites or Online Services for any purpose that is unlawful or prohibited by these Terms. You may not use the Websites or Online Services in any manner that could damage, disable, overburden, disrupt or impair any Cloudflare servers or APIs, or any networks connected to any Cloudflare server or APIs, or that could interfere with any other party's use and enjoyment of any Websites or Online Services. You may not transmit any viruses, worms, defects, Trojan horses, or any items of a destructive nature through your use of Websites or Online Services. You may not exceed or circumvent, or try to exceed or circumvent, limitations on the Websites or Online Services, including on any API calls, or otherwise use the Websites or Online Services in a manner that violates any Cloudflare documentation or user manuals. You may not attempt to gain unauthorized access to any Websites or Online Services, other accounts, computer systems, or networks connected to any Cloudflare server or to any of the Websites or Online Services through hacking, password mining, or any other means. You may not obtain or attempt to obtain any materials or information through any means not intentionally made available through the Websites or Online Services. You may not to use the Websites or Online Services in any way that violates any applicable federal, state, local, or international law or regulation (including, without limitation, any laws regarding the export of data or software to and from the US or other countries).
Cloudflare retains the right (but not the obligation) to block content from its Distributed Web Gateway that Cloudflare determines (in its sole discretion) to be illegal, harmful, or in violation of these Terms. For these purposes, illegal or harmful content includes but is not limited to: (a) content containing, promoting, or facilitating child sexual exploitation and abuse or human trafficking; (b) content that infringes on another person’s intellectual property rights or is otherwise unlawful; (c) content that discloses sensitive personal information, incites or exploits violence, or is intended to defraud the public; and (d) content that seeks to distribute malware, facilitate phishing, or otherwise constitutes technical abuse."