As an open source geek, as a long time MAME user and as someone who contributed around the edges (I cant remember details but I do recall doing something with the Namco System 2 protection back in the day and also some fiddling with Suzuka 8 Hours, I forget whether any of my code actually ended up in MAME though) I actually support the idea of a move to an OSI approved license (although I personally think LGPL3 would have been a better choice than LGPL2) Nothing being done indicates that MAME itself will go commercial or cost money. What this means is that code from other emulators (many of which are already licensed under GPL/LGPL/BSD) can be mixed with code from MAME/MESS.
As far as commercial use goes, can anyone think of a situation where someone would be making commercial use of MAME under a new permissive license who isn't already saying "Screw you" to the devs and violating the license anyway? Someone building a bootleg arcade board or selling a DVD full of ROMs isn't going to care what the license says.