BLUESTAR  Numbers don't appear on the tape as I type and perform calculations. Seems to work in Tiger (10.4.11) but NOT on Leopard (10.5.1). I'm running a Mac Pro Quad Core 3 Ghz with 7 GB of RAM and Leopard (10.5.1)

Also, the developer support form on the website doesn't work when submitting a support email with Firefox (so what do we expect from this developer then as far as a software?...):

Internal Server Error

The server encountered an internal error or misconfiguration and was unable to complete your request.

Please contact the server administrator, jbjovelet@wanadoo.fr and inform them of the time the error occurred, and anything you might have done that may have caused the error.

More information about this error may be available in the server error log.

Apache/2.0.54 (Fedora) Server at www.rubensoft.com Port 80  
(Version 7.0)

BOGDAN  TopCalculette is just great!  
(Version 5.0)

3818  Too expensive! Try Koala Calc, it's free and does more!  
(Version 4.6.3)

ANONYMOUS  $25 for a calculator? Get real!   
(Version 4.6.1)

JIM BISHOP  COOL! Works great with OS X and is very welcome. Nice job. G4, 933, 1.3 Gigs RAM, OS X 10.3.1  
(Version 4.6)

MICHEL L.  The best calculator !

It's a great application you must try !! Not simply a calculator but this is also a powerful converter. Works fine in Panther 10.3.1  
(Version 4.6)

FRANK JANG  This app is not compatible with Mac OS X Panther. A great app but need upgrade very soon.  
(Version 4.0)