Tex-Edit Plus "InterfaceLib" bug with some Mac OS versions

When Walter Sheluk installed/ran Tex-Edit Plus 4.0.2 under Mac OS 8.1, the following error message came up: "The application 'Tex-Edit 4.0.2' could not be opened because 'InterfaceLib--FetchFontInfo' could not be found." Walter could not locate any such file on his drive. Text-Edit Plus 4.0.2 did work fine in Mac OS 8.6. Two other readers have reported the same error, also running Mac OS 8.1. The bug thus appears to be limited to this version of the OS. Update: Tim Mityok gives this detailed explanation of what is going on here: The error "The application 'Tex-Edit 4.0.2' could not be opened because 'InterfaceLib--FetchFontInfo' could not be found" indicates that the program is looking for a program API named "FetchFontInfo" that is not present on that version of Mac OS. InterfaceLib is the Shared Library that is inside the "System File" that PowerPC programs link to in order to access features in the Mac OS using the Toolbox API. When a PowerPC program is launched it is "linked" to InterfaceLib and other libraries that have exported (made publicly available) "symbols" corresponding to< various API functions. If a particular symbol is not found in the specified library you get the error message "The application <name> could not be opened because <missing symbol name> could not be found" and the program quits. This usually occurs on older versions of Mac OS that do not have a specific feature that was added later on. In some cases there is a bug in an older version of Mac OS where a feature was available, but was not "exported" from InterfaceLib and thus it cannot be found, but it may link properly with the newer programming interfaces from Apple. If the software absolutely needs the missing feature then it should be stated that the program requires a minimum OS version that does have the feature and should not be run on earlier (feature unsupported) versions of Mac OS. According to Apple's programming interfaces "FetchFontInfo" is part of Mac OS 8.5 and newer only thus it would work on Mac OS 8.6 and not 8.1. Update: However, Scott Bell replies: "I experienced the same bug running Mac OS 8.5.1." Another reader had the same problem with Mac OS 8.5.1; the vendor sent him a new beta version, which fixed the problem.