The latest version of PixInsight, 1.5.9.561, which we released on November 14th, seems to not work on Mac OS X 10.5.x (Leopard). Of course, it runs fine on Mac OS X 10.6.x (Snow Leopard).
The reason is that build 561 depends on these system libraries:
/usr/lib/libssl.0.9.8.dylib
/usr/lib/libcrypto.0.9.8.dylib
(you can verify this with: otool -L /Applications/PixInsight.app/Contents/MacOS/PixInsight)
Unfortunately, Mac OS X 10.5.x has only the previous versions of these libraries:
/usr/lib/libssl.0.9.7.dylib
/usr/lib/libcrypto.0.9.7.dylib
and Apple, as far as I know, is not updating them —they should, of course!!!.
OS X 10.6.x has both versions, naturally. I'll fix this issue (by including private copies of libssl and libcrypto in the PixInsight.app application bundle). In the meanwhile, there are two solutions:
- Use build 553, released on October 29th.
- Do a bit of system hack. There should be no problem in copying (as root) versions 0.9.8 of both libraries to /usr/lib:
sudo cp libssl.0.9.8.dylib /usr/lib
sudo cp libcrypto.0.9.8.dylib /usr/lib
If someone is interested in trying this, I can upload both files.
Of course, upgrading your Mac to OS X 10.6 Snow Leopard is much easier and much, much better

Sorry for the inconvenience!