It is a bit unusal that the KASToolbar package used by the project has a dependence of the project-specific package doublecmd_common.
KASToolbar is written by me specially for Double Commander. Really doublecmd_common is a general purpose package, it does not have a project-specific only stuff.
Sorry, this was not meant to be some kind of criticism. Just built the Double-Commander, and I see that it is an amazing product!
But one question: you mention that some third-party packages "have a specific patches". Which effect does this have on my system? For example you include a v3.1 of DCPCrypt while the version distributed by OPM is v2.0.4.2. It is a problem in the Lazarus package system that only a single package can exist within the IDE. So, when I write an application needing DCPCrypt I will be using your version after I compiled Double-Commander, and maybe use features which are not available in the "normal" version 2.0.4.2, and when I publish my application as open source users may not be able to compile it because they cannot resolve this dependence (and even I myself may have forgotten about it).
Therefore my suggestion: Rather than adding these modified third-party components to your project as packages could you just set the unit path of the project to point to them. Of course, components in these packages must be created at runtime then. This way a user could use a modified package in addition to an already installed package.