Upspring
From Spring

Upspring
Upspring is a Model Converter/Editor for the Spring RTS Engine.
supported formats:
[.s3o]
[.3do]
.3ds
.obj
.opk
.c3o
Download
Win32 installer:
Source Code:
Common Issues
http://answers.springlobby.info/questions/690/why-does-upspring-mirror-my-model-when-i-import
http://answers.springlobby.info/questions/398/upspring-how-to-set-piece-origin