Gullet
Gullet is a proof-of-concept Javascript based window manager that runs within the web page itself, allowing for other HTML pages (hosted on the same server) to be displayed within windows in the web page. This is a proof-of-concept as I haven't found any real practicle use for Gullet over traditional web navigation methods, but hey, maybe you will.
These windows can be moved, closed, rescaled, and are fully functional assuming that both Gullet and the page are configured correctly.
There is a readme on how to get Gullet set up on your own site, as well as example pages that show it already set up and configured.
License
This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with this program. If not, see https://www.gnu.org/licenses/.