ihasmail is webmail: it is nearly always run as a network service rather
than handed to anyone as a binary, which is the case the plain GPL does
not reach. The AGPL's section 13 does — anyone running a modified
ihasmail for other people has to offer them its source.
LICENSE is the full AGPL-3.0 text from gnu.org. The SPDX identifier
changes from GPL-3.0-or-later to AGPL-3.0-or-later in package.json, the
lockfile's own entry for it, and the About screen. Old commits and tags
are left exactly as they were; this is the license from here on.
The LICENSE file only carried the short "how to apply" notice, not the
license itself, so it wasn't a valid GPLv3 distribution and license
detection tools couldn't identify it. Replace it with the canonical
674-line GNU GPL v3 text (sha256 8ceb4b9e...), and move the project
copyright line plus the "version 3 or any later version" grant into the
README, which now matches package.json's GPL-3.0-or-later.