WebAssist does not charge for bug fixes. Like i said in my initial reply, the fix to a bug may come in one of two ways: a new "dot" release, or a Known Issues fix.
Dot releases are free upgrades, and Known Issues fixes are in the Download Center with instructions on how to apply the fix.
If you have encountered a bug, you should create a new thread in the forums to make sure we know about it, and we'll see what we can do about getting it fixed.