No it doesn't mean that devices below that version can't run WebWorks apps. There are too many variables between device hardware, OS versions, Apps and SDKs to keep such a chart. Bugs are almost never universal for all apps - if an app crashes it doesn't mean that all apps crash.
Note that WebWorks only works with version 5.0+ of the OS anyway. OS 4.x doesn't have the necessary low level APIs to support them.
The amount of memory available for WebWorks apps is heavily dependent on the hardware, and somewhat dependent on the OS. Many OS5 devices have 256MB of RAM, and for those that are upgradeable to OS6 that is just barely enough to run the new WebKit browser. Later OS6 devices are mostly 512MB and many OS7 devices have 768MB. That makes the biggest difference, though improvements in WebKit and the OS make small differences as well.
Tim Windsor
Application Development Consultant
