I'd suggest going after source compatibility rather than binaries. It shouldn't be that difficult to check an Xcode project for things incompatible with GNUStep and offer a way to allow ProjectCenter to build binaries on and to other platforms, provided the developer refrained to use Mac-only features. It would be a nice way to collect hard data on what should be considered more important for GNUStep to develop, generating countless other opportunities for students pursuing various degrees.

BTW, is anyone building TextMate for platforms other than OSX?