From the user's perspective its easy to say: it looks simple, so why shouldn't it be simple to maintain? I don't think its reasonable to compare Synergy to other projects unless you've actually tried to develop the code.
I'm not really sure how we can come across as a large company, there's only 2 of us right now.
Actually we're charging because we need to. Charging a small fee allows us to hire more programmers. We are not charging "just because we can". For the last 2 years we have made progress from donations, but not fast enough. Every new OS version introduces new bugs into Synergy, faster than we can fix them. The bottom line is, we need more software engineers and this is the only way to do that.
We tried that a while ago. It turns out, around 90% of Synergy users are very technical (fellow Software Engineers and the like). Often technical people aren't that interested in support because they prefer to figure stuff out for themselves (because we find it fun). Synergy does have a private help desk that Synergy users can contact for troubleshooting, but users that contact the help desk are often less technical (when it comes to Synergy troubleshooting).
Most Synergy users don't use repos, or Linux for that matter, so this new model works for Synergy (though, it probably wouldn't so well for a Linux-only project). Also, repos tend to have much older versions (at least in Synergy's case).