MacDailyNews Note: Apple Macs have had rounded corners since their inception. Mac OS 7.6, released January 7, 1997, did away with the rounded corners on the bottom (along with the “System” moniker).
“Displaperture,” from developer Many Tricks, brings back rounded screen corners to Mac OS X 10.5 Leopard.
Users can decide which corners they wish to be rounded off, choose their radii, and enjoy their Macs the way Macs were meant to be.
Displaperture is a universal binary and free for download (if you like it, the developer accepts donations).
More info and download link here.