They seem to have restricted free players to Trooper, Tank, Raider, and Light Artillery as well as only being able to use 3 maps.
I am trying out an alternative (Advance Wars By Web) with my cousin today, so I will be back with results/opinions/tell you guys my opinion on which is better (AWBW seems to have more units and maps anyway).
EDIT! : Advance Wars By Web has much more units to be used, as well as having things like attack/defense/other bonuses depending on the CO you choose/play as (this is exactly like Advance Wars on the GBA).
Maps are bigger and strategies are much more varied due to the inclusion of COs and their respective powers (such as base capture speed bonuses).
The layout of the site is much more cluttered and not as clean/newbie friendly to navigate through as compared to WeeWar's. However, there is no "Pro"/pay-to-get-better-units thing involved. Sign up and play!
That said I think this is a much more technical and strategic type of game, so those who like their speedy attack units (like the Raider in WeeWar), or artillery users can choose the CO that best fits their playing style.
Here is the link:
http://awbw.amarriner.com/
Would be better to communicate with players on some IM client like MSN, because this site does not have an in-browser chat like WeeWar.
My name on AWBW is superjs. If people actually sign up for this then I will make a separate topic so it does not kind mushed into this one.