Whether it is legal or not completely depends on HP's stance regarding their old calculators. They have allowed the calcs ROMS to be used in emulators, if I am not mistake, so they may no longer care.
You would have to contact HP regarding the issue. It is no longer a copyright issue if HP give the go ahead.
Joe
They tend to be more "possessive" of their current offerings.
Isn't the 12C still "current"? I just bought one off the shelf a couple of months ago.
That was my point. This guy is selling a PDF version of the HP-12C manual while the 12c is still a currently sold product.
Gene
HP 12C still at Office Depot for $79. Was not but 10 or so months ago they were begging at Walmart on markdowns for 30$!