Amend check_commit and PR template

Require GPLv3 license and check for violations.

.github/pull_request_template.md

@@ -8,6 +8,7 @@ The following must be true before PRs can be merged:
 * Commits in a single PR should be related.
 * Major new features or bug fixes should reference a [CHIRP issue](https://chirp.danplanet.com/projects/chirp/issues).
 * New drivers should be accompanied by a test image in `tests/images` (except for thin aliases where the driver is sufficiently tested already).
+* All files must be GPLv3 licensed or contain no license verbiage. No additional restrictions can be placed on the usage (i.e. such as noncommercial).
 
 Please also follow these guidelines:
 

tools/check_commit.sh

@@ -1,6 +1,6 @@
 #!/bin/bash
 
-BASE="$1"
+BASE=${1:-origin/master}
 RETCODE=0
 
 RED='\033[1;31m'
@@ -14,6 +14,7 @@ function fail() {
 
 echo -e "${GREEN}Checking from $(git rev-parse --short ${BASE}):${NC}"
 git log --pretty=oneline --no-merges --abbrev-commit ${BASE}..
+echo
 
 git diff ${BASE}.. '*.py' | grep '^+' > added_lines
 
@@ -53,6 +54,11 @@ if grep '/cpep8.blacklist' added_lines; then
     fail 'Do not add new files to cpep8.blacklist'
 fi
 
+grep -i 'license' added_lines > license_lines
+if grep -iv '(GNU General Public License|Free Software Foundation)' license_lines; then
+    fail 'Files must be GPLv3 licensed (or not contain any license language)'
+fi
+
 for file in $(git diff --name-only ${BASE}..); do
     if file $file | grep -q CRLF; then
         fail "$file : Files should be LF (Unix) format, not CR (Mac) or CRLF (Windows)"