Copyright? Public domain? Vintage? Is this an area of confusion?

I have fallen fast for the art of knitting. I have stumbled into a hobby that has turned into a way of expression like no other. As with other knitters when I find an old pattern at the library or a consignment shop I get the goose bumps and the wheels of my brain start spinning in purl, garter fever. But can I use these patterns for more than my own personal use? This question is as complicated as a fine spun spider web. I turned to my good friend the google search bar and found a couple of sites that I found to be useful. The first being http://books.google.com/googlebooks/copyrightsearch.html. This is a very detailed list of copyrights and file for extensions. If a pattern is more than 28 years old and it has not renewed its copyright it is known as free public domain. In other words you can use the pattern as you see fit. If it has been renewed it falls under the 50 to 75 year mark before it is public domain. This however, gets even more complex because the photographs are under their own copyright. The second site was very handy for the basic understanding, http://knitty.com/ISSUEfall03/FEATcopyright.html As for me, I can rationalize my time spent on this hobby! If I was into rock climbing I would explore the trails and parks that allow me this sport. I would also spend time researching the best equipment. The best attire. I wouldn't want to climb without full knowledge of what I am doing. So knitting is a full hobby that not only fills my heart with joy but it also spreads joy to the ones I knit for. A win win scenario. To even conquer this quest further I rely on my grandchildrens smiles, laughter, and hugs to keep me knitting. I mean you simply can not as a Grandma not knit for those cutie pies !!!! So the next time you walk by an estate sale stop on in and take a look around you may just find the next knitting treasure! Happy knitting.