- Add zetacoin-qt.desktop to the `source` and `sha256sums` arrays.
They were already added, do you mean zetacoin-qt-git.install?
Whoops, I misread the PKGBUILD. Ignore my suggestion. No, you do not need to add zetacoin-qt-git.install to the `source` and `sha256sums` arrays.
- Add a function named `pkgver` to the PKGBUILD file.  This function
will allow `makepkg` to update the version number automatically,
you of the need to update the version number by hand.
Added the same one that mesa-git uses, would it serve?
The `pkgver` you added is OK, but it could be better. The zetacoin git repository has tagged releases, and the wiki states: 
It is recommended to have following version format: *RELEASE.rREVISION*[...]
Here's a better command for generating a package version number:
git describe --long | sed -E 's/([^-]*-g)/r\1/;s/-/./g'
That command generates the following version number:
- Consider explicitly `cd`-ing into the `$srcdir` directory. Though this
step is not strictly necessary, it makes your intent more clear to others reading through the PKGBUILD. As a Python programmer would say, "Explicit is better than implicit."
Here I'm afraid that I'm not following you. What do you mean with 'cd'-ing explicitly?
Consider adding `cd "$srcdir"` to the beginning of the `package()` function.
Please excuse my use of bastardized english. I could have worded my suggestion more clearly.
- Consider removing the "miniupnpc" dependency from the package.
warns that it is not necessary. Do not remote the dependency blindly, though: namcap is sometimes wrong about dependencies.
I have removed the 'miniupnpc' dependency and recompiled it, it didn't complain. I have this package installed and it seems to work, so I think it may be safe to remove it.
The bitcoin docs discuss how to build bitcoin on unix.  (zetacoin is based on bitcoin, so the bitcoin docs should be relevant) They state:
miniupnpc may be used for UPnP port mapping. It can be downloaded from
here. UPnP support is compiled in and turned off by default.
Also, namcap complains about the zetacoin-qt-git package if miniupnpc is not listed as a dependency:
zetacoin-qt-git E: Dependency miniupnpc detected and not included
(libraries ['usr/lib/libminiupnpc.so.9'] needed in files ['usr/bin/zetacoin-qt'])
These two facts indicate that miniupnpc should be included as a dependency. I suggest adding a comment to the top of the PKGBUILD explaining why miniupnpc is included as a dependency.