About GNU, GPL, LGPL,FOSS etc.

I dont understand if I can or not use third soft components I'd want to add to my commercial application.
I read and read and read GNU and GPL (are the same?) and LGPL, BSD; MIT ... and I have not any conclusion (I'm very confused)
Starting at the point my appplication are going to be commercial, what can and cannot I do whith the 'free' licenses types ?
What about my own development ? It can exist two uses :
1.- I use third component (exe, lib + source code or full source code)
2.- I use full source code and I have modified some parts.

The check list is then :
--------- Use exe/dll ---- Full source code ---- Modified source code
GPL
LGPL
FOSS
MIT
BSD

And the answer for each item :
- Yes: You can use totally free.
- No1: You have to redistribute your whole own software
- No2: You have to redistribute only the modified original source code

And whats about the obligation to show copyright ?
- Yes : You have to show a GNU/LGPL/etc copyright text.
- No1 : You only have to inform that you use a third component by its name.
- No2: You have not to show no copyright neither references.

Can anybody fill the list ? Thanks

If you application is going to be commercial, then I would always recommend strongly that you consult a lawyer to give you advice.

Taking legal advice from a forum is a bad decision and could get you sued. Best to talk to someone who specialises in software licenses. If they are wrong, then you can sue them for any losses.

I have to agree with squidge here. Legal interpretations gleaned from the Internet carry no guarantees, and particularly when dealing with the latest versions of the GPL, LGPL or anything at all from the FSF or Dick Stallman it is mandatory to consult an attorney; these sources of software carry agreements that are deliberately written to be obscure and vague, and are designed to entrap companies who enter into those agreements in expensive lawsuits aimed at 1) shaking settlement fees out of them to support the activities of the FSF and 2) gain control of proprietary software.

In fact, the rule at our company now is: if it's licensed under the newest LGPL or GPL, don't use it, period. And this is from a large company with attorneys on staff.

But seek out your own legal counsel. It's a swamp.

Thanks both