There may be a reason why only few people used Semagic on Mac: WINE needed Xcode to be installed. It is 4GB in size. I installed it but then standard instructions did not work for me and Semagic was not working.
Also I installed Winebottler but it did not install ie6 which is required for WYSIWYG editor.
Then I found
PlayOnMac and it seem to work just as on Linux.
PlayOnMac is about 150M in size, download, open, drag Playonmac to the application folder shortcut, run Playonmac, install Semagic selecting libraries for it: vcrun6, ie6, riched30, msxml3 (the same ones as on Linux).
What does not work is drag-n-drop of images from explorer. For image upload, select 0 upload block in the upload options in the upload window for Scrapbook (Journal/Pictures/Open Scrapbook/Options). Use Ctrl+F12 to type non-English letters in HTML mode. To use msxml parser (to post to Blogger and Wordpress) open Playonmac, Configure, select Semagic on the left, select WINE, Configure WINE, Libraries and add msxml3 override.
This text is written by Semagic running on OSX Lion in WYSIWYG mode.
Screenshot (uploaded from Mac):
If you get "Invalid password" error when viewing history: uncheck challenge-response authentication in Options/Advanced. That is LJ error but it is not fixed yet.
http://semagic.sourceforge.net Update 25 Oct 2012:
After some update of Playonmac, MFC42u.dll and riched20.dll sometimes are not found and Semagic does not run after installation. Select Configure->Miscellaneous->Open program directory, open windows/system32 and place those files there. You can find those files via google. Also one user reports that Semagic kept crashing for him in Linux until he found in google msls31.dll and put it into Semagic and System folder.