Assimp is released as Open Source under the terms of a 3-clause BSD license.
Copyright (c) 2006-2012 assimp team
All rights reserved.
Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:
- Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
- Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
- Neither the name of the assimp team nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.
An exception applies to all test models in Assimp's repository. They're generally free for testing and private use, but not necessarily for commercial use. There's usually an accompanying info file containing detailed license information.