"Horsepower Lab 1D" package is distributed under terms of this LICENSE. In short, you may freely copy the unregistered version, but please be warned that it can be used only for evaluation (it produces wrong simulation results).
Registering your copy (one license per computer) turns the program into production mode. Finding out if the registration has already been done is simple -- (1) check that there's no Register menu item in the main application menu or (2) read output of the solver program.
"Horsepower Lab 1D" is provided "as is" without warranty of any kind, expressed or implied, including but not limited to the warranties of merchantability, fitness for a particular purpose and non-infringement. In no event shall its author be liable for any claim, damages or other liability, whether in an action of contract, tort or otherwise, arising from, out of or in connection with "Horsepower Lab 1D" or the use or other dealings in "Horsepower Lab 1D".