Basically common sense and respect.
You are free to use the free or pro version of CleanMem for personal or corporate use.
You are free to distribute CleanMem as long as you do not change it in anyway, make it look like it is your own or include it with another program. If you distribute CleanMem you must make it clear that it is a program by itself and by PcWinTech.com.
Don't change or mod CleanMem itself. Such as hacking the program and modding it to look different. Changing settings is of course just fine.
Don't make CleanMem look like it was created by or belongs to someone else.
And pretty much anything else that falls under common sense and respect.