Always nice to see such concern...
In fact, it turns out the last .NET version for Vista was not 4.6.1, but 4.6, wich, if dates are anything to go by, should mean the last LB version to be usable under Vista should be something around maybe 5.5 or 5.6 - however, indeed, it does state on the website that Vista is supported, which seems to be downright untrue, and to have been so for a while.
Now, that said, with the understanding that Vista is not receiving any more updates, and nor is the last working LB version, I imagine it might be possible to put it up for those hanging on to Vista for another while (trust me, all my emulators work well enough as is), but that is, after all, the developer's decision.
Well, and I'd like to thank everyone who posted supportively in this thread, lots of fun with your gaming.