If there is an accident (and there will always be accidents), you as a user of opensource-FCs are responsible for the software/hardware, and if you are not skilled to develop FC-software your are already almost in prison (since it is careless from you to develop something you have no idea about with opensource FC you develop as you use). Every opensource FC-software does state, "development only, your own risk only". Not useable for commercial operators, please that does not mean that others are better, it is more or less a legal issue, a matter of responsibility.
Opensource in the past really was great, but now is seems to become another wording for "no support", "I don´t care", "I can use all of that", ... . Especially at universities there are graveyards of opensource software which nobody is able to use. The project is over, and the software was good to get the final report, but no lasting contribution.
And if you really want to earn money with something that uses opensource software, you cannot earn enough money you will need for the lawyers clearing the IP for your product (and responsibility). Now here are tow strategies to overcome this:
a) you do not care, which works if you stay small enough, if your business explodes, they (the lawyers) will toast you.
b) do not use a single line of open-source software rewrite every single piece. (no even a jpeglib or a zlib)
Possibly the developers behind run the opensource-world, but they make the world turning also within another environment. (And there is always ONE developer behind)
best regards
Ferdinand