RankGuru SEO 2.21 for Mac was available to download from the developer's website when we last checked. We cannot confirm if there is a free download of this app available. We recommend checking the downloaded files with any free antivirus. The actual developer of this software for Mac is Sandra Marisa Paoloni. The program lies within Developer Tools, more precisely Webmaster Tools.
From the developer:
RankGuru allows you to easily check how well your website is performing, by automatically retrieving your rankings per keyword. It lets you export your ranking history to CSV, and use your favorite data analysis tool. You can quickly check trends by looking at the progress semaphore.
You may want to check out more software for Mac, such as Screaming Frog SEO Spider, Bitnami SEO Panel or SEO Tool for iWeb, which might be related to RankGuru SEO.