[texhax] LaTeX legal help

[Uwe Lueck]

Tonight (CEST) Alojzy Leszcz wrote:
> The thing is I've spent some time searching on the 
> net for answers to my question but haven't found 
> any 100% sure response yet.

100% legally are hard.

> I've been writing a book with LaTeX (Windows, MikTeX)
> which I plan to put on my website and sell it (only pdf,
> no plans to benefit from sources). Could you please tell
> me what's the best place to post questions about
> dos & donts with using LaTeX commercially ?

In principle, you must enquire about every "piece" or 
"package" (an entity that has an entry http://ctan.org/pkg/..., 
or what has a line in the MiKTeX Package Manager, alternatively 

    https://miktex.org/packages

) you are using what license it has.

For CTAN packages such as "txfonts", you find the license
on
   http://ctan.org/pkg/txfonts

If anything you use apart from direct Microsoft software
comes from MiKTeX, you can get about 99%% from

    https://miktex.org/copying

where Christian Schenk starts "To the best of my knowledge,
all software in this distribution is freely redistributable".
(Alas, that is 2017 ...)

HTH -- Uwe.