I don't have the time to check what it is but dimok posted this with r529

*Added Alternate DOL support which is used to boot games that don't work due to
IOS Reloads like Mortal Kombat

NOTE: There is a GameSettings you need to turn ON to load Alternate DOLs. The
alternate DOL has to be called 6 IDs .dol for example RHDP8P.dol and has to be
in the root of the SD. Giantpune will add custom path support i dont have time
for it.

If you want to use it use r533+ (custom path is supported)

giantpune also said:

Also, before you start asking about the dol replacement deal, please read
http://gbatemp.net/index.php?showtopic=160710
It is also discussed a little bit here
http://gbatemp.net/index.php?showtopic=158884&st=135
If you still don't understand it, then this feature is not for you
and those games were not meant to be played on your wii.

Here is a "How To" For running Medal of Honor Heroes 2 from USB Loader GX with alternative dol:
http://gbatemp.net/index.php?s=&showtopic=149922&view=findpost&p=2057212

Here is a step by step that starstremr put together on how to use and extract the alt dols.
http://gbatemp.net/index.php?showtopic=161988