Do all Macs have expander capabilities?

[RGould8 at aol.com]

If I wanted to create a Revolution app for Mac OS X that downloads a .sitx 
file, could I write a routine that would pass that downloaded file to Stuffit 
Expander for decompression?

I guess before I can go that route, I need to ask this - - - - do all Mac OS 
X systems come with Stuffit Expander?

If not, can anyone tell me what unix calls come with Mac OS X that can be 
used to compress/decompress Mac OS X applications, while preserving the 
resource-forks?