> You can link some libraries statically and the rest dynamically. GlibC, in particular, is remarkably stable and it's easy to support older distributions with older versions of GlibC via LSB.
Good point, thanks!
> Yet you solve this somehow for MacOS
By providing an application bundle, which is a standardized procedure and something users expect. Also, (ABI-stable) system libraries are not copied to the application bundle. So, the bundle only contains a fraction of the used libraries (Qt and DBXML).
> and Windows
Again, here we use standard libraries (VS2008 redistributable), and drop Qt/DBXML DLLs in the same directory as the executable and it works perfectly on Windows XP and up (probably also Windows 2000, but we didn't check), although the software is compiled on Windows 7.
> (last time I've checked Windows had no DB XML support)
There's Windows support for DB XML. Oracle offers pre-built DLLs, or a source archive with Visual Studio project files. We use the latter, and building the DLLs with Visual Studio 2008 is just one click.