It seems too easy to use one of them within your software product. But, be aware of the license.
- Yahoo! UI Library: Rich Text Editor
- Free Rich Text Editor
- Offered under a Creative Commons Attribution 2.5 Generic license
- Offered under a LGPL license, also known as the GNU Lesser General Public License, former GNU Library Public License.
- Offered under the GPL, LGPL and MPL open source licenses but an Closed Distribution License - CDL is also available
- Offered under the original htmlarea licence, essentially this is a BSD style licence