When I bought the game back in 5th grade, it was quite hard for me to scrounge up 20 bucks for a game that i've been demo-ing for a couple months.
I think that if the game were to be made free-to-play it would receive a lot more attention, for:
a) Showing up on Steam as a F2P game garners a bit more attention from gamers that aren't looking for a commitment
b) Allows a bit more easy access to younger/perhaps target age people (Cause it's a lego game.)
Really, I don't know if Badspot is making a lot of revenue from the game. I mean, the last really major update, correct me if I'm wrong, was 4 years ago. Seeing that he isn't really doing a lot to add to the game makes me wonder if he's working on better, more profitable projects rather from BL. (If I'm incorrect and Badspot does do routine improvements on the game, then this is a moot point) Honestly, I have nothing wrong if he really is letting BL sit there and make money for him. However, I think that if the game were F2P it would vastly increase the playerbase.
Just something I was thinking about