Freeware in XAMPP

[NumOpen]

I wanted to add XAMPP into next version of COMPILIBRE (http://www.numopen.fr/compilibre), but I can't because it contains a freeware : Mercury Mail Server.
Could it be replaced by a free software ?

[Nobbie]

What is the difference between "free software" and "freeware"? Sorry for my stupid question, but i cannot determine what you are going for.