No, it means that you would just need to re-register to get another registration key for another 14 months of updates.
I take it that you mean Aug 1 2010 in both cases as you have mentioned two different dates, Aug and April.
Your situation with win98 however, is more complex as I don't know exactly how long support for win98 in the form of avast 4.8 will last though, avast is one of the last AVs that I know of which still support it.
avast 5 is in beta testing right now and that doesn't support win9.x or winME. Originally on the web site it stated to the end of this year, but that may change as one of the Alwil team personally thought it could be longer, possibly 6-12 months after the release of version 5.0. That however, was a personal opinion and not an official statement.
