Tuleap can take quite some time to load the user interface, here are some key points that could be improved:
1- Number of requests
In order to load my planning view, Tuleap makes 51 requests to the server, among them, there are 1 html page, 19 javascript files, 18 css files, some resources (images, fonts, etc) and a couple of XMLHttpRequests. All the JavaScript files and the CSS files could be concatenated to have only one of each in order to reduce the number of requests.
2 - Usage of the compression
Using gzip compression, you could reduce the size of the Javascript and CSS downloaded by about two thirds (1.2MB). The use of gzip on some files like planning-v2.js could save 370KB (which is almost the size of 15 of your other JavaScript files).
3 - Use browser caching
None of your Javascript files, CSS files or font is cached by the browser, including files which will not change like jquery-2.1.1.min.js or bootstrap-tooltip.js etc. On top of the two previous pieces of information, this could speed up dramatically the user experience for a Tuleap user.
4 - Optimize the order of the styles and scripts
Most of your Javascript and CSS files are in the document head, in order to improve the performances of the loading of the page, you should include external CSS before external Javascript and include the Javascript at the bottom of the body.
5 - Minimize all your Javascript and CSS code
All your Javascript and CSS files are not minimized, as such files like "themes/FlaminParrot/js/motd.js" or "project-privacy-tooltip.js" may have most of their content composed of comments then code. Most of the bootstrap code is not minimized too (button, dropdown, modal, popover, tooltip) and some of the JQuery code too.
6 - Usage of your CSS
Most of the content of your CSS files is not used by your site, you could trim some of the CSS to reduce the size of your CSS file and speed up the loading of your pages.
You can find attached to this issue a HAR file with the trace of the loading of the planning view of tuleap.net which you can analyze using the website
http://www.softwareishard.com/har/viewer/. I have found those issues on both tuleap.net and on tuleap.eclipse.org.