Add DISCLAIMER, LICENSE and NOTICE files.

The content of COPYING is duplicated in LICENSE, so it got deleted.

Author: Ouss4

COPYING

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+Apache NuttX is an effort undergoing incubation at The Apache Software Foundation (ASF), 
+sponsored by the Apache Incubator. Incubation is required of all newly accepted projects 
+until a further review indicates that the infrastructure, communications, and decision 
+making process have stabilized in a manner consistent with other successful ASF projects. 
+While incubation status is not necessarily a reflection of the completeness or stability 
+of the code, it does indicate that the project has yet to be fully endorsed by the ASF.
+
+Some of the incubating project's releases may not be fully compliant with ASF policy. For 
+example, releases may have incomplete or un-reviewed licensing conditions. What follows is 
+a list of known issues the project is currently aware of (note that this list, by definition, 
+is likely to be incomplete): 
+
+ * Releases may have incomplete licensing conditions.
+
+If you are planning to incorporate this work into your product/project, please be aware that
+you will need to conduct a thorough licensing review to determine the overall implications of 
+including this work. For the current status of this project through the Apache Incubator 
+visit: https://incubator.apache.org/projects/nuttx.html