Check IRC or something to ask around how you could help with things.
(The repo is quite stalled... all you can see is translation updates.
Not sure about the official stance on this.)
Emiliano Canedo wrote:
> Hello all!
> I'm new in this list; I'm a long time user of XFCE, and a unix/linux
> developer. I want contrib with this project. Where is the repo of code?
> Xfc-dev mailing list
> [hidden email] > https://mail.xfce.org/mailman/listinfo/xfc-dev