The files really are damaged. In fact, Erik Barzeski reported having problems with certain other third-party extensions because of these damaged files. According to Hrvoje Budin, "it looks like Open Transport installer is making those damages during install process, because checking uninstalled OT files on Mac OS 8 Update image reports no errors."
Fortunately (as has been the case in previous similar instances of this), Apple's ResEdit should be able to fix the problem. Just launch it and open the damaged files. It should report that it made "minor repairs." Save the changes when closing the file and it should be okay. Nathan Raymond adds: "By default the Verify option under the File menu in ResEdit will check and repair a file, if it can. Additionally, by holding down the Option key while selecting Verify you can see the normally hidden details of the resource scan and repair. In the case of all these files, ResEdit reported "bad file length", which it was able to repair."