You may use the decompiled/reconstructed vanilla source files in your mod without explicit permission. You must give us, the SkyUI team, credit when doing so. While we are not the original authors of this code, decompiling and fixing it up again took a lot of work that deserves mentioning.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
Thanks to MIT license for providing this standard disclaimer.
Thanks to Bethesda Game Studios for creating The Elder Scrolls V: Skyrim, providing the base content and allowing us to mod it.