This all depends on their copyright status and whether you have registered them. If a font is FreeWare or Public Domain, you may freely use and publish the font. If a font is classified as ShareWare, you must register the font before using it. In most cases, registering is as simple as sending the author a few bucks. This is a very important concept to understand.
ALL fonts have authors.
People have painstakingly created these fonts for our use and enjoyment. Most often, the authors won't even let you use the font until they get money. These people have released their fonts for us to try. If you like and use a shareware font, you MUST pay the author the fee described in the text file. You may use them however you wish, but the author still retains copyright and you cannot edit the fonts.