Here are some brief notes about OpenSimulator's directory structure. Unfortunately, due to historical reasons, most files are currently stored in the bin/ directory where libraries (DLLs), configuration and cached data is all lumped together.
This is correct as of the binary distribution of OpenSimulator 0.7.4. A source code distribution will have more directories to contain the source code files. These are not required to actually run OpenSimulator after it has been built.
This document covers only directories. It could be usefully extended to cover the files as well.
Addon modules for opensim source code can be placed here. These will be built along with the core OpenSimulator code with the "nant build" command (after running prebuild.sh for the first time). See the README in this directory for more details (need more information about this on the wiki).
Effectively OpenSimulator's main directory. More information about this below.
All OpenSimulator admin/user/dev documentation is on the http://opensimulator.org website. However, the doxygen.conf file in this directory can be used to generate source code documentation. See the README for more details.
Minor miscellaneous information files.
Licenses for third-party libraries used by OpenSimulator
Cache folder generated by Mono.Addins. This can safely be deleted, though that means it will just be regenerated by OpenSimulator on its next run. This is used by both the simulator and ROBUST.
Location for third-party binary addon modules for OpenSimulator. See README for more details (need more information about this on the wiki). This is currently used only by the simulator. If not present then it will be ignored.
Location for asset files that are cached on disk if this facility is enabled (it is by default). This can be deleted, though it will be repopulated over time by the asset cache if enabled. This is used only by the simulator.
Default assets loaded into the simulator. These are used for items in the OpenSimulator library and in default avatar construction, among other things. Used only by the simulator.
Configuration files included by the OpenSim.ini file. Used only by the simulator.
A few data files, chiefly the list of default avatar animations (avataranimations.xml) and prototype files in support of the WebStats ajax facilities. Used only by the simulator.
Data files for constructing the items in the avatar library. Used only by the simulator.
Cache of decoded JPEG2000 information for efficiency. Can safely be deleted (it will be rebuilt when next used). Used only by the simulator.
32-bit native code libraries used by OpenSimulator on Linux, Mac OSX and Windows. Currently used only by the simulator though this is not guaranteed in the future.
64-bit native code libraries used by OpenSimulator on Linux, Mac OSX and Windows. Currently used only by the simulator though this is not guaranteed in the future.
Used by the CoreModules/LibraryModule to add IARs as avatar inventory items on startup. Undocumented at this point. Currently used only by the simulator.
Storage place for maptiles generated for return to Linden version 3 viewers and related third-party viewers. Used by the simulator in standalone mode and by Robust.
OpenSimulator physics c# code. Used only by the simulator.
Region configuration data. Used only the simulator.
Script engine cache area. Used only by the simulator.