Don,
I want to clarify what I think I understand about copyright.
The exact source code to OpenACS is definitly copyrighted just like any code. The actual tables aren't.
What I mean by that is that if I take a copy of OpenACS and create my tables then I have to abide by GPL. However, if I read documentation, or simply do a dump of another system (like you suggested), I think the courts will say that this is information as opposed to intellectual property and that is the key difference. I could also keep the table names the same (names can't be copyrighted) and rebuild the plpgsql (which would have to be done anyway in whatever sqlserver uses). The only compatibility really needs to be with the actual tables and the rest can be clean roomed very easily. I certainly wasn't suggesting that they would just steal our code. All they need are the tables.
Of course as you say, it is all really academic in the fact that MS has already proven it can do what it wants, and if 5 years from now there is a remedy so what, they will already own the market.