The client can only generate Small (128x64x128) Medium (256x64x256) and Large (512x64x512) worlds due to UI (User Interface) limitations currently. However McForge-Redux or compatible servers can send much larger worlds to the client because I increased the available memory to storing the world. In the 0.3 version coming up, this will all have changed so 'hopefully' after the UI redesign I will be able to add more buttons to the generate world menu. The current limitation is that the UI source is obfusticated and hard to work with but once I finish rewriting the core UI it should be easy to add more buttons.
Have you thought about working with ClassiCube? They've already deobfuscated most of the source code so it's easier to work with, and the community is probably a lot more active than MC Classic is these days.
Been working on some improvements, mainly performance to get FPS boost on low end laptops. Trying to aim this game at low end computer users that can't play regular minecraft. Computers that can't play regular minecraft CAN play this even if PIXEL FORMAT NOT ACCELERATED because there is a software rendering fallback. On a lot of low end computers and laptops you will see FPS for 100+ and on a mid range desktop you will see 300-600 and on a high end developer's machine you can see FPS of way over 1000 and reaching 2000.
Multiplayer support has been ditched for the next release, overall stability improvements and lots of features from ClassiCube and WoM client have been added, daylight cycle removed (its classic after all).
And yes we are very close to a release. Mac users will appreciate the double click to run .JAR file.