Further to the discussion at http://netsparkle.codeplex.com/discussions/284936
which gives an idea of how to target .Net 3.5 I believe it may possible to take this one stage further (further backwards!) and target .Net 2.0
Referencing the LinqBridge library at http://code.google.com/p/linqbridge/downloads/list
either as source code or binary and changing the target framework to 2.0 in the Project files at least allows the library to compile correctly. There is one very easy change to make the code in the constructor of NetSparkleAssemblyReflectionAccessor().
I don't know this library well and running the test applications fails but I think that is due to an unresolved URL rather than inherent issues with this approach.
Would be keen to hear if this looks viable