I can't answer all of your questions (only Lynn can) but I can answer some.
For changing companies see a previous post in this section for the answer.
It does NOT line up at all. The new product will essentially be a new piece of software. Different SQL, different language, different GUI, not open-source, no API's, and there will be some concessions on the part of any current DBA customer who wants to convert as to what data CAN be converted. Some transactional data will NOT be able to be converted at all. Therefore, in those aspects you would be starting with some "opening balances" type of thing. So said Mike in our last conversation about 3 weeks ago, anyway.
Multi-threaded DOES mean you can have multiple windows open with NO fear.
I doubt very much that ISTS is going to invest any time/resources into Linux versioning as there are probably about 4-5 sites in the 3500+ total that have anything linux. The payback would be pretty small.
That IS is Mozilla issue.
Applications in this price range are VERY seldom multi-monitor aware and capable. It is time consuming to program and test, and again, an incredibly small number of clients would ever have need for this capability.
The rest I leave to Lynn.