I just got a summons today.
The charge off date was 09-30-99. The open date was 1-30-00
This company purchased the debt on 9-30-06
Is this past the SOL?

First its not a good idea to piggyback your question on someone else's. This can lead to confusion. You should start a new thread. So I've moved your question to its own thread.

SOL's vary from state to state so its impossible for us to tell you since you didn't say WHERE you are.

How can a debt be opened AFTER the charge off date? Depending on where you are, the important date is either the date of last activity or the date of default. Neither of which is listed.

Finally, if a suit was filed (indicated by the issuance of a summons), then its likely the plaintiff has provided some proof that they are within the SOL. Otherwise, the suit shouldn't have been filed. But even if they are past the SOL that doesn't mean you don't have to pay, it just means they can't sue.