Ripoff by a smug, arrogant developer who reviews his own products with 5 stars. Went from free to .99 to 3.99 what an absolute F%(*&^%^*hole. Why Macupdate allows it to remain is questionable at best.
1/2 star is too high. He can always buy some shill reviewers to pump it up. All yur star are belong to us!
Still not working on 10.10 and no disclaimer anywhere near by. If you need to mute your startup chime, Cocktail does the job indeed as suggested by user Ean. Onyx has a mute option but that doesn't work on 10.10 as well.
Turning off the startup sound is not a good idea. This tone is there for a reason. The Mac does a series of system tests before each startup. If everything tests OK then you hear the chime. If not, you will hear different tones, depending upon what is wrong. This is a great aid in troubleshooting an ailing Mac. Just accept this chime as your Mac saying it's happy and ready to do your bidding.