IIRC, JS support is built into MWLL.
And the software to build a league site is quite complex. Forurms are easy - many pre-made packages out there. The league software is a different story. Take a look at MWL. You would have to join as a member, but it's worth looking at. The ladders and various forms of league play (PL, TB, Solaris, Racing, CTF, McRug, etc, etc) coupled with the unit rosters, battle control/challenges, etc make this a very non-trivial matter.
MWL had the great fortune of having a wonderful coder build it from scratch (Neuromancer, now passed away, RIP). Gladius and others have full control of the site now, but it is still a big task to maintain.
Now, adding a MWLL ladder would be pretty straightforward.
