Adobe Premiere Pro CC 2015 is proprietary, commercial software. Although it is old, it is not "abandonware." The copyright is still strictly enforced by Adobe. Using a pirated version for client work opens you up to potential lawsuits and criminal charges. If you are a freelancer or a business, the risk to your reputation and legal standing is not worth the price of a subscription.
Macs are not immune to viruses. Unverified .dmg or .pkg files from third-party sources are a primary vector for: Adobe Premiere Pro Cc 2015 Free Download For Mac