NO - no deployment to the GAC is necessary, Orchard uses local bin deployment, and each module and theme has its own local bin for any of its dependencies - this is the bit missing when trying to run the website from the source zip.
It's the same advice as before - I can replicate the error by unzipping the Source file, opening the Orchard Solution and running Orchard.Web. Orchard builds the modules with exceptions - it cannot resolve the dependencies, Lucene.Net.dll, MarkdownSharp.dll, ICSharpCode.SharpZipLib.dll,
etc,, as expected they do not exist within the website - I had not built Lucene, Markdown, Orchard.Media, Orchard.Comments, etc, in VS, only Orchard.Web (and dependencies).
It may look like you have built all the necessary projects - browsing the folders you will find bin directories under each module but look closely and you may only find copies of dlls from the website root bin folder (Orchard.Web\bin) no module dll or other
dependant dlls from the lib folder.
That is the reason I suggested you check the dlls are in the correct folder in the website - they will only be there if you have built all the modules in VS (Build Solution Ctrl+Shift+B) or unzipped and copied a module package - check for the existence
...Orchard.Web\Modules\Lucene\bin\Lucene.Net.dll (not Lucene.dll)
...Orchard.Web\Modules\Markdown\bin\MarkdownSharp.dll (not Markdown.dll)
These files will only exist from a source deployment if you have used VS to build, at least once, each Module, that has dlls dependencies other than Orchard core - this will copy the dependent dlls from the lib folders to the relevant Module bin folder.
Take a look at Orchard.Web.zip which is pre-built ready for deployment to a server - each module has a bin folder with the necessary dependant dlls - the same as installing from a package.
If the dependant dlls are not in bin folder of the module itself the dynamic loader will not be able to find them when the application is run in the web server - it can only see folders within the website (Orchard.Web is the root) to resolve dependencies,
not the lib folders which are part of the source zip file accessible to VS but external to the website. The dynamic load process tries to resolve all the project references to files local to the web app.
In the case of Lucene the dynamic loader will attempt copy Lucene.Net.dll from ~/Modules/Lucene/bin to ~/App_Data/Dependencies.
Building the Lucene module and running Orchard.Web again - Lucene.Net.dll is not longer reported as missing and is copied along with Lucene.dll to ~/App_Data/Dependencies.