Linux would be in the same boat as a Mac version. As far as I know, it should be possible to make. However, since each platform requires some additional changes, it's not something I can quickly get done. Since I haven't even looked into the specifics of Linux's quirks with regards to what JRNL needs, it would be developed after a Mac version was built.
And to reiterate, the Mac version is still very much up in the air as of right now.
-Saul