Harmonise GPL license to GPL-2 or later (#19003)
Link to issue number:
#18574
Summary of the issue:
Updating NVDA license from GPL-2 to GPL-2 or later. Full details: #18574
Description of user facing changes:
n/a
Description of developer facing changes:
copying.txt file updated to GPL-2 or later, and addition of GPL-3 T&Cs
