"Patch Welcome"

No, it's not a nice way to say "go away!", rather an indication that at least some kind of initial stab at a solution would be useful to get something started.

For unscheduled tickets, the requirements are a bit stronger: as no Trac developer has shown interest in making the bug or feature request part of the Trac roadmap, the patch has to be very convincing: well exposed rationale for the change, clarity and correctness of the code, unit tests, etc. See TracDev/SubmittingPatches#Whatisagoodpatch for more.