Here are 2 patches related to logfile rotation.

The first is a Windows-specific bug that would cause the logfile to never be rotated.
Windows does not update file meta-data (like file size) until the file is fsync'ed.
This patch calls fsync() on the fd before querying size, so that the actual size is returned.
https://github.com/garret-smith/yaws/commit/317008a49b945b8cb534463fbb3a8cfb8fe69a9c

The second is a general fix to rotate the logfile regardless of the copy_error_log setting.
According to the manual, (http://yaws.hyber.org/yman.yaws?page=yaws.conf) setting copy_error_log to false should not prevent logfile rotation.
https://github.com/garret-smith/yaws/commit/2411b2f894506b8cb1247aa6e8f629b594b8a52f

Thanks,
Garret