Great work Jason
I found a few issues.
I'll start with the biggest in my opinion and that is that I can't actually start a game in BBM
Actually that's not accurate. I can run Steam and PC games fine, just nothing that uses an emulator.
That was the biggie.
Next up, BBM displays platforms that were deleted. As an example, I had a TODO platform which I used when messing with some Steam games not long ago. I deleted it and it is not visible in LB, but it is right there in BBM. If I try to access it I just get a black screen because there is no data to display.
I guess BBM uses LB's settings for fanart? In my instance of LB for PC games I currently have the fanart set to a single default image. In BBM this results in no fanart whatsoever in the games list. You might want to allow for different settings for both LB and BBM.
NOTE: Fanart displays fine in my other instance of LB.
Also, while I am on the subject of artwork, you should have some default images where no artwork is found. You should probably add Platform images for Steam, Origin, GoG, Uplay, etc. for people who split them up like I do. (I suppose this falls on me slightly)
Gameboy Color is missing its banner.
The 'open folder' option does nothing for Steam games, you might want to remove it.
The 'open emulator' option fails when a script is set as an emulator. There is probably very little you can do about this, but it is probably worth remembering for future troubleshooting. Maybe you could add an option to set an emulator path in the platforms manager for when this is the case. Using scripts is common with some arcade emulators. It is very common for me since I point LB to scripts and not emulators.
Overall, I was pleasently suprised how slick it actually is. I had very little lag with one exception, flipping the box art. This took a second or two, which felt like a minute or two, you know. But other than that, really fluid. Oh, slight jerks when scrolling the list fast but not as bad as I was expecting.
That's all I found so far.
No wait, one more little thing, the mouse cursor does not disappear when using the controller. Minor I know, but it irritates the heck out of me when games, videos, media centers, etc. do that
That's all. Excellent work, brilliant alpha.