Looks similar to IE to me except you have tabs at the side most of the same commands seem to be there
It's a Mac--running on a PC!! 8^)
Actually, that's the SheepShaver emulator running. SheepShaver is a program that fully emulates a PowerPC Mac computer--however, the latest OS it can run is 9.04.
I picked up a copy of the OS at a rummage sale and then managed to make a CD image to use with the software--then installed it to a raw disk image (800MB).
Currently, I store this disk image on my USB stick (compressed, 92 MB)
OS 8.6 comes with IE 4.5 for Mac--and if you look carefully, the thread shown in the browser is in fact this Singles Thread 8^)