gutcheck was written by Jim Tinsley and has been used by both Project Gutenberg and Distributed Proofreaders for many years.
Recently, the possibility of producing a new version has been discussed. Since it is clearly very important that any new version should be compatible with the original (that is, find and report all the true positive warnings that gutcheck does on a given e-text), the first step is to create a testsuite.
To that end, the latest alpha of bookloupe version 2 (version 1.52) has been created, which has no changes to gutcheck itself but contains a test framework and the beginnings of a compatibility testsuite.
Resources and other links: