Propel 1.5, the next version to be released later this month, will no longer be published under a LGPL3 License, but under the more liberal MIT license. This change removes a usage restriction enforced by the LGPL3: you no longer need to release any modifications to the core Propel source code under a LGPL compatible license. Propel users still have the right to use, copy, modify, merge, publish, distribute, sublicense, and/or sell Propel. In other terms, you can do whatever you want with the Propel code, without worrying about the license, as long as you leave the LICENSE file within.
Found a typo ? Something is wrong in this documentation ? Just fork and edit it !