It depends whether you mean the software runs without access to the internet or whether you can obtain the software without access to the internet. For good or ill, most software is distributed through the internet.
However, TeXLive, an implementation of Tex for most platforms, and that includes lualatex and Gregorio for typesetting chant, is available on DVD (if you can still read those) from the Tex Users Group, in addition to being available for free download on the internet. See:
It does not require the internet to run, although updates and bug fixes are delivered that way. There is a major overhaul annually.
Is there any software that can typeset Gregorian Chant music without access to the Internet?