This is a question received recently but it crops up now and then, so here it is as an FAQ:
‘I’m considering buying MacStitch and I wanted to make sure first whether I’m allowed to sell patterns made with it on Etsy and other marketplaces and if there is any special version requirement for it. Thanks in advance, A’

Answer: Of course you are! We don’t even ask you to mention the software you use. Loads of people are doing it, and you don’t need any special version, although the Premium edition has better tools for generating PDF files. Good luck!