For what it’s worth, it doesn’t look too bad.
Assuming you are still working on this, I think that a BeOS/Haiku style of UI is a better choice than copying Windows 8+ or macOS. It might not be everyone’s cup of tea, but at least it has a distinctly different feel to it.
Abbreviating your project’s name as ‘SDE’ would seem slightly ambiguous. Is there a better or preferred short form? You know like StarDE or STDE. There might be a name conflict out there for something like AsteriskDE or ADE, but if you mean “star” like the keyboard symbol, that would be appropriate.
Tangentially, your website could use a little bit of cleanup in my opinion.
For example:
The download icon is still a local file reference on the page for your manual viewer application (6-4 helpmeman.gambas).
On the first Applications page (6. Applications) you have a link claiming to point to www.gambaslinux.fr that actually tries to go to http://operation.andre.free.fr/star/www.gambaslinux.fr, which obviously doesn’t exist.
P.S.
Why would you use the GNU FDL for a software project? A desktop environment isn’t a document after all.
