A lot of ship are modified by a lot of people in Orbiter
if it's only small modif I don't think anyone will get upset,
if it's big modif you just need to ask the author and give credit
in your release documentation. I don't see any difference beetween a free
fs panel and a free Orbiter panel if the author is ok there is no problem.
For the stock DG you may ask Frying tiger as for the shuttlA
for others ship, I dont know.
I worked on the dg panel because I was just planning to add
one or two button for my private use and I finally ended with the DGIII
But If you plan a big project perhaps you may better start from complete scratch.
drawing a new panel isn't difficult. the most challenging is to program the logic
behind it. FS gauge don't work at all in Orbiter it's a completely different system.
I know that there is a panel SDK but I never tried it so I don't know
if you can do many things with it, otherwise you should work
with C++ and the panel SDK.
Dan