Change to just file LICENSE, add @source for CTIS data

Author: brookslogan

DESCRIPTION

@@ -8,7 +8,7 @@ Description: This package contains data sets used to compile vignettes and
     other documentation in Delphi R Packages. The goal is to avoid calls
     to the Delphi Epidata API, and deposit some examples here for easy
     offline use.
-License: MIT + file LICENSE
+License: file LICENSE
 Depends:
     R (>= 2.10)
 Suggests: 

LICENSE

@@ -1,2 +1,2 @@
-YEAR: 2023
-COPYRIGHT HOLDER: epidatasets authors
+This contains a collection of data from different sources under different
+licenses; please see the documentation for each object for license information.

LICENSE.md

@@ -65,6 +65,23 @@
 #' during the COVID-19 Pandemic and downloaded from the CMU Delphi COVIDcast
 #' Epidata API. This data set covers the period from
 #' June to December 2021.
+#'
+#' @source Data from Delphi COVIDcast. Obtained via the Delphi Epidata API.
+#'   \url{https://cmu-delphi.github.io/delphi-epidata/api/covidcast.html}. This
+#'   object contains a modified part of the
+#'   \href{https://cmu-delphi.github.io/delphi-epidata/symptom-survey/#covid-19-trends-and-impact-survey}{data
+#'   aggregations in the API} that are prepared from the
+#'   \href{https://www.pnas.org/doi/full/10.1073/pnas.2111454118}{COVID-19
+#'   Trends and Impact Survey}; see the first link for more information on
+#'   citing in publications. These aggregations are licensed under the terms of
+#'   the \href{https://creativecommons.org/licenses/by/4.0/}{Creative Commons
+#'   Attribution license}.
+#'
+#' Modifications:
+#' * Selected a small subset of the available data.
+#' * Changed to wide format.
+#'
+#' Delphi Group at Carnegie Mellon University
 "ctis_covid_behaviours"
 
 #' COVID-19 Incident Cases and Deaths