Man, I've been running Linux on a desktop (on and off, mostly on) since 2009 and I haven't ever paid for an application. Sure, I've paid support / development applications, have donated $, and have paid for SAAS, but never a standalone application. I'm not trying to discourage you or anything of the sorts. Just seller beware of your market and target audience.

I saw a comment below on self contained .tar. I think that's a really smart way to go. Or, make it Debian / LTS Ubuntu and a RHEL package. Support the big two. If anyone runs arch or something like that make them compile it themselves or ldd the binary.