Graphics drivers aren't open source either. A very large amount of actual Mac OS X performance problems and crashes come from the combination of the graphics drivers and CoreGraphics/Aqua. Both of these systems can use main memory and therefore might be influencing or be influenced by paging issues.

If you can get a reproducible case and capture enough useful diagnostic information you can give that to Apple to try to get a fix in some future version of OS X. Have a look at /usr/bin/sysdiagnose and /usr/sbin/spindump among other tools. I'm sure there are more diagnostic tools internal to Apple, which would require that you have a case that is reproducible from a new OS X install rather than from a system with files copied over. If you can identify the one file from ~/Library or wherever that triggers it, then you can pass that along as the repro case.

In general people (like me) just don't have the time to hunt down every crash, hang, etc. we find when using a computer. So I can understand if one doesn't bother with capturing diagnostics and repro cases or with downloading Darwin or Android source to debug a crash. I can also understand where huge frustrated discussions like this one come from. But deep down there is an answer, and it likely is not from some huge corporate failing on Apple's part.