Geekbench 3 is no longer the current version of the software, and Primate Labs typically requires a paid license for its "Pro" features. However, there are legitimate ways to access and use it:
Primate Labs offers a fully functional of Geekbench 6 that allows you to run benchmarks without a license key. The only limitation is that you cannot submit results to the online browser. geekbench 3 license key free
Geekbench operates on a "freemium" model, meaning you don't necessarily need a license key to run basic benchmarks. Geekbench 3 is no longer the current version