Founder and Lead Developer for Magic Hat Software LLC, creators of Irth Online.

Irth Online is a modern Massive Multiplayer Online Role Playing Game built from the ground up on the latest technologies. It creates a virtual reality environment rich in detail and interaction.
Please check out the screen shots section chronicling the early to late development of Irth.

The Irth Engine was built by Magic Hat Software for both Irth Online and licensing to 3rd parties.
Some of the technical specs for the engine are:

Server:

• Multi Server, Multi Processor, Multi Threaded, cluster of Windows PC’s
• Configured via ODBC connected database. (tested on Microsoft SQL and MySQL)
• Optional configuration of world objects via database, registry and/or scripts.
• Scripting and world event handling via DLL plugins, COM, Grayscript, Javascript, and LUA.
• Dynamic geographic load balancing across nodes in the cluster.
• Networking via TCP and UDP using a proprietary SOAP like object protocol.
• Compressed/Encrypted(via RC4) data channel with challenge/shared secret login
• Object/method/property granularity of security (per role) on all objects.

Client:

• Cascaded level of detail for truly HUGE seamless worlds. 1024KM x 1024KM
• Seeded/compressed or randomly created detail for organic world content.
• DirectX9 with shader 1.1 and 2.0 plugins for special effects such as water reflection, volumetric fog, etc.
• Scene optimization via loose octree and integrated hardware based occlusion.
• Skinnable in-game user interface.
• All GUI dialogs built using the Windows Dialog resource editor.
• DirectSound 3d audio support.
• Uses both Cal3d and EmotionFX character animation systems.
• IDV SpeedTree tree rendering
• In-client world editor for ‘instant play testing’ of world changes.

Tools:

• Property browser application connects to the client or server. All world objects may be interrogated for properties and methods.
• Microsoft Access Database forms library for configuration of all world systems.
• Integrated Subversion (version control) management of scripts and system resources.

External Libraries Used:

• OpenJPEG for loading and saving of JPeg2000 files
• Javascript - Spidermonkey javascript scripting
• Lua v5.1 (with easyLua) - Scripting.
• ZLib - File compression
• BZip2 - Data compression
• ODE - Physics system
• Cal3d - Characters
• EmotionFX - Characters
• IDV SpeedTree - Rendered trees
• Subversion - For version control of scripts/resources among multiple developers/world builders.
• Microsoft Libraries - Win32, DirectX9, COM/ATL, etc.

Comparable (mostly) Game Engines:

• Shark3d - very flexible tools, server and client.
• BigWorld Engine - both server and client. Very impressive feature list.
• Emergent Games Engine - just a client (Gamebryo), server engine in development. (details are sketchy)
• Irrlicht - open source client
• Darkstar - Open source java based engine. Not really very comparable, but interesting.