Ok so if you modify an open source software. And then decide to sale the newly modified open source software. It's legal to do so. But do you have to include the original unmodified software source code for the buyer? Also do you have to tell the buyer that it was from an open source software? So my question pretty much is how does selling modified open source softwares work? Reason i'm asking, is because I plan to build some addons for some open source softwares and maybe want to sell them. Thank you.
Depends what it's licensed under (GPL, Creative Commons) I guess, I know a few you'll be expected to provide the source code at least if it's asked for, and it doesn't hurt to tell them it was from open source, but once again, some licenses will require you do
Answering in order those 3: If by this you mean the original code and your code. No. Your code will fall under the license of whatever the parent source code had on it. You must give them all of that code(which includes the code you used, not separate as part of your new package) if you sell or distribute it. Exception to this would be the BSD/Apache/Artistic(Perl is under this) style licenses which only require the copyright notice remain. To the best of my knowledge, you don't have to tell them where it came from. I would tell them if they asked. Again BSD licenses, I can state there isn't anything in that short simple license about notification. It is overly complex and everyone has different opinions about how it works. No one really knows. Why? Cause it hasn't gone to court(TTBOMK). I would put the disclaimer up, IANAL, but I would put good money on the fact 99% of the lawyers in the US have little understanding of open source software and lots of it is information through disinformation.