I've read in this thread that "more writing means restriction".

    Also that a GPL software could no longer be saled.

    That's all obvious.

    The restriction in the GPL are restrictions to the possibilities of
the saler to restrict the rights of the user. GPL is there to favor the
user's liberty versus the saler's. Freedom for one means restrictions
for the other.

    It is legitimate to make a living from your work, but, in this
case, GPL isn't for it. But you can use freely GPLd tools for it.

    GPL is for the case you want to *donate* your work, give total
freedom to the user and make sure nobody can ever take away this freedom.

    I'm retired. I develop software for my own use. When I think it may
be of interest for others, I publish it with a GPL license. I don't mean
to make a living ffrom it: I got a pension.

--     Didier