Well, lets take each item here:
Yes. DNN 4.4.1 is written in .NET 2.0, with VS 2005.
Yes the gallery 3.0.12/3.1.12 is written in .NET 1.1, with VS 2003. You will need those tools installed on your machine if you want to compile/debug the gallery module. You can not compile the Gallery 3.x version with VS 2005.
If you copy the gallery module .NET 1.1 code into your DNN directory, you will not be able to compile your DNN 4.x source tree anymore as it has .NET 1.1 code in it. If you want to compile the DNN 4.x directory, you will need to _only_ copy the binaries into the DNN 4.x directory. That means you will need to put the Gallery code into some other directory, compile the gallery code there, then copy the compiled files (dll, aspx, etc) to the DNN 4.x directory and run the DNN code there.
As you can see compiling a .NET 1.1 module (eg. the Gallery) in a .NET 2.0 project (eg. the DNN 4.x source) is a major pain in the butt. So when I went to work on the code, the first thing that I did was convert the Gallery .NET 1.1 code to .NET 2.0 so that I could compile/debug everything as one nice project. Keep in mind that the "upgrade wizard" did little to help in the upgrade and I spent about a day or so working on the code to convert it (and I've been doing ASP.NET development since the beta versions of .NET) I'm not sure why you would want to waste your time converting the code, especially since there are so many bugs in it anyway. The new official gallery module is based on my conversion to .NET 2.0 and should be comming out soon. Originally it was going to come out January 2007 (yes 2007), so we'll see how it goes.
The Gallery module 3.x or 4.x do not use a DAL. It stores settings in the standard DNN config way and application/file/image data is stored in a XML file.
The survey module is a DNN 4.x module (.NET 2.0) It integrates much better with .NET 2.0 VS2005. The little standard that DNN uses is that modules written for DNN 3.x (.NET 1.1) are versioned 3.x and modules for DNN 4.x (.NET 2.0) are versioned 4.x.
Hope that helps.