Hello Kris and welcome to the ArtRage forums
No, AR mostly uses it’s own .prs format for brushes. It can use .abr brushes, though they need a bit of setting after installing. But that’s probably a topic for another time!
With these Custom Brush presets, once you have unzipped the download you need to put the 2 folders; SLR Painters and SLR Texture Brushes into the Custom Brush presets folder in AR.
To do this, launch AR6 and in the Menubar go to; Tools > Brows Content Folders > Tool Presets…
In the window that opens find the 'Custom Brush' folder and place the two new folders containing the presets in there.
Now relaunch AR6 and the SLR brushes will be available from the Presets Panel when using the Custom Brush.