Licensing open source programs is too complicated. I have started off with the GPL for zsync, as I had expected to use more code from rsync. However, I only took one file, and that turned out to be buggy so I have dumped it.

But now I'm using OpenSSL, but strictly speaking the OpenSSL license is not GPL compatible. I could switch to a BSD license, but I would still have to abide by OpenSSL's old-BSD-style advertising clause — fair enough, they have the right to put it in there, but it would make zsync out-of-bounds for linking to GPL projects.

So I dropped the only fragment of rsync code and it is time to drop the OpenSSL dependency too. It was a rather heavy compile-time dependency anyway, considering I only needed the checksumming code (at run time it only required libcrypto, which was less of a problem). I looked around and found the code from md5sum in OpenBSD, which looks just the ticket. And, as a gesture in favour of more liberal licenses like the zlib license (which thankfully has no problematic restrictions), I will probably go to something like the Artistic license for zsync-0.1.0.