Background: We have a non-spatial reporting web application with a SQL Server backend. We would like to add a spatial component to this application: serve up some basemaps, serve up points and polygons for view and editing, build reports for selected polygons.
To that end, the plan is to use ArcSDE with SQL Server, and use ArcServer to serve up base layers and vector geometries. (something like WMS/WFS-T)
Problem: We may, at some point, decide we want to move away from expensive proprietary software, and use a FOSS alternative (e.g. GeoServer, or TinyOWS if/when it supports SQL Server). If possible, I'd like to avoid building the application irrevocably around ESRI technology.
My understanding of SDE is that it can either use ESRI specific spatial formats, or spatial formats native to the database system it's installed on. (I presume there is some performance penalty for using the native formats.)
My Question(s): If we were to set up SDE on this SQL server database using native SQL Server spatial formats, would we be able to set up say, GeoServer, to run against the tables that SDE was managing? What would it take to rip SDE out and use something else? (Also, a meta-question: is this a reasonable question to be asking? Is there something important I'm missing?)