Ariba.com isn't a full website in the traditional sense. Type the address into your browser and you'll immediately be taken to SAP's official page for spend management software. That redirect is the key to understanding this domain. It's been owned by SAP for years, and the domain's history goes back to 1997.
For a redirect domain, the important questions are about security and ownership. Both check out here. The SSL certificate is valid, the domain is not blacklisted, and the registration details are transparent. The long Web Archive history confirms it's been a legitimate business domain for decades. There's no reason to treat ariba.com as a scam or fake site. If you see a link to ariba.com, know that it will take you to a legitimate SAP product page. That's all it does.