So summarizing the obstacles that I encountered when compiling under Ubuntu:
Problem: With mbuild, the file csharp/ICT/PetraTools/_bin/Debug/Ict.Tools.NAntTasks.dll was not found.
Workaround: This file should have been build with nant. Use Xbuild.
Problem: Nant is too old ...
(use nightly build)
Problem: Is compiling, but errors like The name `StreamUtils' does not exist in the current context or similar I/O Erros.
Solution: Update SharpZipLib.dll
Problem: ICSharpCode.SharpZipLib.dll not found
Solution: This file is available in the source zip, so make sure you run this command gacutil with the current working directory of the extracted sources.
Problem: The password of which user??
Solution: Standard Admin user, so root in case of mysql and postgres in the case of PostgreSQL. This will be used to create user & database called "openpetra".
Problem: Server.config not found (System.ApplicationException: Unable to load the configuration file './etc/Server.config'.)
Solution: Make the OpenPetraRoot.dir of OpenPetra.build.config absolute, delete the generated Server.config and compile again.
I will edit the wiki according to these. I'm also thinking about writing some script to have a simple ./config && make && sudo make install installation process (as usual in Linux.)