Anyone who has browsed a lot in the source trees of Slackware will have seen this comment from Pat about the source code for the kernels used in Slackware?
Has anyone ever found any concrete examples of this?

I found one that should be especially interesting to ZipSlack users and serves as an example of what 'not patched kernels, but not exactly virgin either' means.

Found this kind of by accident. On my site I have one distro available that's not really mine -a tiny, hard-to-find distro based on Slackware-3.3. ZipSlackers take note -when you run this, the /DOS directory is fully read-write! You don't get that with modern ZipSlack. After wondering about it and even trying to get in touch with the UMSDOS maintainer, I finally 'diffed' a few files in the /fs subdir of the kernel source and found where Pat changes the code to disable this -probably just replaces the files with hand-edited copies he has, since these are parts of the code which don't change very often.

Anyway, if you use ZipSlack and would like your /DOS directory to be writable (that's where you see any files on your partition that are not part of ZipSlack) and you know how to compile a kernel from source, just use the virgin source code from kernel.org, compile with the ZipSlack config file and you should now be able to write to the /DOS directory.
If you'd like to preserve Pat's other kernel hacks, you could just substitute the files from the Slackware kernel source with the ones from the virgin source.

That's cool, but I think it's best to keep it read only, considering that the idea of zipslack was to have the linux install not distrupt any other OS installed on the same partition.