I think he meant to say 30 - the game comes with a default 16-team American league, a 10-team Canadian league, and a 4-team indoor league. Unless there's a 31st team that's not in any league so you can just play around with the creation features.
There are 5 indoor teams as an example how the game would run an uneven schedule.
Maybe release the sourcecode for just the uniform editor
That would be illegal, because the game has no built in editor, and I doubt that Matrix Games could release the source code to Photo Shop or Paint Shop Pro. [;)]
Any .bmp editor can be used to make uniforms, including MS Paint that is built into Windows, but using a program with layers is easier to use because textures can be added without drawing them for each uniform.
What's the point of including a 16-team American league? We're all going to have to make it 32, or some other number? Why not just let us create all the teams ourselves?
A 16 team league is much easier to manage. The NFL has 32 teams, but this is not an NFL emulator. It is almost just as easy to add new teams as it is to modify the teams to any specific league.
Some people will want to play some games first before trying to create teams.
That's about it. A 32 team league takes a long time to sim a week of games rather than a 16 team league. Some people will want to cut that down to an eight team league just to get the feel of the game.