Add LICENSE File and Clarify Licensing Information

[porkfriday]

The repository lacks a LICENSE file and contains insufficient information about licensing terms for both the code and model weights. While the README acknowledges that PixArt model weights are derived from the open-source project PixArt-alpha, it doesn't specify the license for the RelaCtrl codebase itself.

Impact

Without clear licensing information:

1. Users cannot determine if they can legally use, modify, or distribute the code
2. Commercial applications may be uncertain about legal compliance
3. Contributors might be hesitant to submit pull requests

Proposed Solution

1. Add a LICENSE file to the repository root with an appropriate open-source license
2. Update the README with a dedicated "License" section that clearly states:
   • The license for the RelaCtrl codebase
   • The license for the model weights
   • Any third-party components and their respective licenses
3. Ensure that license information is consistent with dependencies and models used

Common open-source licenses for ML projects include MIT, Apache 2.0, or GPL, depending on the desired level of openness and restrictions.

[MaAo]

Thank you for your attention. This project is licensed under the Apache 2.0 License.