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This sounds very interesting, but with some comment
you say "I wanted to release kind of a modified version of XOOPS". Do you mean a complete XOOPS package? Or some hacks? If you mean a complete version of xoops, my guess is the developers here would be very interested to see your concepts. Ideally we work as a collaborative community here, where we share development that ultimately benefits the project as a whole. Optimisation of course is a major part of that, but we wouldn't want to release a fork version, would we?
Providing you keep within the terms of the GNU GPL license, of course, you have no restrictions.
Optimisation is a valuable topic, so let's see what you've got.