If I understand well, because of the nature of accessing embedded dlls it is impossible to use the mono dllmap feature to use the library on mono.
If there would be a version which would ship the dlls as non-embedded files, it would be simple to map to the apropriate .so files on Linux.
Comments: I forked the project to https://magick.codeplex.com/SourceControl/network/forks/yothsoggoth/magicknet and I've done some work there to add support for OS X. The managed .NET parts didn't require any changes as Mono handles that just fine. The only part that needed to be modified is the native library, which required a couple of minor code changes to support non-Windows platforms. I've added the Xcode project to the repo, which is setup to build a native .dylib, which can be switched in place of the .Native.DLL and DLLImport will find it just fine. Building on OS X requires building ImageMagick from source (or finding existing libs for the desired arch) and either having the necessary libs installed on the machine (libjpeg, libpng, etc. - see http://www.imagemagick.org/script/advanced-unix-installation.php) to build statically or linking dynamically against ImageMagick and shipping the dylib for that instead.
If there would be a version which would ship the dlls as non-embedded files, it would be simple to map to the apropriate .so files on Linux.
Comments: I forked the project to https://magick.codeplex.com/SourceControl/network/forks/yothsoggoth/magicknet and I've done some work there to add support for OS X. The managed .NET parts didn't require any changes as Mono handles that just fine. The only part that needed to be modified is the native library, which required a couple of minor code changes to support non-Windows platforms. I've added the Xcode project to the repo, which is setup to build a native .dylib, which can be switched in place of the .Native.DLL and DLLImport will find it just fine. Building on OS X requires building ImageMagick from source (or finding existing libs for the desired arch) and either having the necessary libs installed on the machine (libjpeg, libpng, etc. - see http://www.imagemagick.org/script/advanced-unix-installation.php) to build statically or linking dynamically against ImageMagick and shipping the dylib for that instead.