(Note: this text is written for and directed at Big Muscle. Just pointing it out in case that the "you"s looks a bit wierd to you (the person reading this text))
Let me first get the most important thing out of the way: You CAN make money with open source software. In many ways actually:
You can charge for the convenicance of auto updates
You can charge for direct support (for example, via email or via a private discord chat)
You can charge for the convenicance of having an already compiled binary version (which is especially true on windows; on linux for example, you usually git clone the repo, cd into it and type `make && sudo make install` and that's it. On Windows though...)
You can make (optional) donations
Speaking of donations: what you offer on your website, those are NOT donations. Those are payments. It is NOT freeware. You just get a free demo version. A donation is something optional. The point of a donation is not to get something back from it (besides maybe the knowladge of having helped someone/-thing or maybe getting a "Thank you" mail from them), but purely to support someone/-thing. And I want to mention that that is the only reason why I actually paid 5 bucks for it: not because I care about the watermark (if that would be my only reason, I could have just used a cracked version, and yes, I DID have a working one back then, but I didn't use it), but because I want this project to stay alive. In other words: I am pretty shure that a lot of peole donated just for support, or at least partially.
Anyways, I of course know that there are not only positive things about open sourceing this software, namely:
You may not make the exact same amount of money from "donations"*
You may unveal your secrets*
However, both of these arguments are very weak. The first one I already talked about above. For the second one: opening this app would mean that a lot more developers could integrate it (as in making their app compatible with it, not as in stealing your code; the only app I know of that supports aero glass is Winstep Nexus, and that one only works when it really wants to, which, as a dev explained to me, is not their fault). It would allow other people to learn about windows from (because, as described on glass8.eu, it uses undocumented windows features). TL;DR both arguments are... bad.
Now let's finally get to why I think it should be open sourced:
You (Big Muscle) are not able to maintain this on your own, or at least not in a way that I would concider acceptable for a paid app. Often times, this app gets a fix about 1-2 months before the next major update comes out, which will break it again. And again. And again.
This app would be accessable to a lot more people.
It would improve the user experiance since it will allow updates to be completed much, much faster.
You would not have to stem this project all on your own anymore, which, again, you're not able to. Almost the entire forum is just "It doesn't work" posts.
As described previosly, third party compatibility could also be improved massively.
A concern you may have is others missusing your code to make money on. This is actually not a problem. You can either use the GNU GPL (or similar), which will technically not prevent your code from being commericallized, but since every modification that is being made availably has to also be opensourced under the same license (or a newer version), it is very unrealistic to think that someone would actually do it, exept maybe in those ***** bundles. While some apps (like OpenOffice or 7-zip, see here ) do suffer from this problem, I, again, don't think that such a tool like AeroGlass would really suffer from this. Alternatively, you can also write your own license, for example like this (this is not legal advaise):
Of course, the above mentiond "license" is only one of many ways it could be done (and, again, it is not legal advise).
I hope that you will change your mind about this program and it's licensing and distribution, as it would gain both you and even more so it's community. Cheers.