Demoware

Demoware is software to recommend a commercial product. 

An example. A company develops a database manager in
order to control the expenditure. Of course this company
wants to show the world how perfect this is. On the other
hand, the company doesn't want to distribute the program
for free. Demoware is a fine alternative then.
It's a version of the program that works for, let's 
say, only a month.

Demoware is in copyright and it is the editor who 
controls the ditribution of it. Most of the time it is 
for free but it is clearly different from Public Domain.
You are not allowed to change it and it is not a complete
program like Freeware.

Demoware is a nice alternative. 
A negative side of it: you have a good idea about your 
program, but you are not able to really know your program 
until you've bought it.